diff --git a/src/auth/mech-winbind.c b/src/auth/mech-winbind.c
index c9e1450f0b..4a65696105 100644
--- a/src/auth/mech-winbind.c
+++ b/src/auth/mech-winbind.c
@@ -180,7 +180,8 @@ do_auth_continue(struct auth_request *auth_request,
 			  str_data(str), str_len(str)) < 0 ||
 	    o_stream_flush(request->winbind->out_pipe) < 0) {
 		auth_request_log_error(auth_request, AUTH_SUBSYS_MECH,
-				       "write(out_pipe) failed: %m");
+			"write(out_pipe) failed: %s",
+			o_stream_get_error(request->winbind->out_pipe));
 		return HR_RESTART;
 	}
 	request->continued = FALSE;
diff --git a/src/auth/userdb-passwd-file.c b/src/auth/userdb-passwd-file.c
index b578d272b6..f80cac1f9e 100644
--- a/src/auth/userdb-passwd-file.c
+++ b/src/auth/userdb-passwd-file.c
@@ -139,7 +139,8 @@ static void passwd_file_iterate_next(struct userdb_iterate_context *_ctx)
 			break;
 		}
 		if (line == NULL && ctx->input->stream_errno != 0) {
-			i_error("read(%s) failed: %m", ctx->path);
+			i_error("read(%s) failed: %s", ctx->path,
+				i_stream_get_error(ctx->input));
 			_ctx->failed = TRUE;
 		}
 	}
diff --git a/src/director/director-connection.c b/src/director/director-connection.c
index a727658efd..2beb327073 100644
--- a/src/director/director-connection.c
+++ b/src/director/director-connection.c
@@ -2051,9 +2051,10 @@ void director_connection_send(struct director_connection *conn,
 	} T_END;
 	ret = o_stream_send(conn->output, data, len);
 	if (ret != (off_t)len) {
-		if (ret < 0)
-			i_error("director(%s): write() failed: %m", conn->name);
-		else {
+		if (ret < 0) {
+			i_error("director(%s): write() failed: %s", conn->name,
+				o_stream_get_error(conn->output));
+		} else {
 			i_error("director(%s): Output buffer full, "
 				"disconnecting", conn->name);
 		}
diff --git a/src/doveadm/doveadm-director.c b/src/doveadm/doveadm-director.c
index 76accd2566..383a62c4a3 100644
--- a/src/doveadm/doveadm-director.c
+++ b/src/doveadm/doveadm-director.c
@@ -60,11 +60,12 @@ static void director_connect(struct director_context *ctx)
 	line = i_stream_read_next_line(ctx->input);
 	alarm(0);
 	if (line == NULL) {
-		if (ctx->input->stream_errno != 0)
-			i_fatal("read(%s) failed: %m", ctx->socket_path);
-		else if (ctx->input->eof)
+		if (ctx->input->stream_errno != 0) {
+			i_fatal("read(%s) failed: %s", ctx->socket_path,
+				i_stream_get_error(ctx->input));
+		} else if (ctx->input->eof) {
 			i_fatal("%s disconnected", ctx->socket_path);
-		else {
+		} else {
 			i_fatal("read(%s) timed out (is director configured?)",
 				ctx->socket_path);
 		}
@@ -79,8 +80,10 @@ static void director_connect(struct director_context *ctx)
 static void director_disconnect(struct director_context *ctx)
 {
 	if (ctx->input != NULL) {
-		if (ctx->input->stream_errno != 0)
-			i_fatal("read(%s) failed: %m", ctx->socket_path);
+		if (ctx->input->stream_errno != 0) {
+			i_fatal("read(%s) failed: %s", ctx->socket_path,
+				i_stream_get_error(ctx->input));
+		}
 		i_stream_destroy(&ctx->input);
 	}
 }
diff --git a/src/doveadm/doveadm-penalty.c b/src/doveadm/doveadm-penalty.c
index 36b9fd85f4..2a4b33d887 100644
--- a/src/doveadm/doveadm-penalty.c
+++ b/src/doveadm/doveadm-penalty.c
@@ -80,8 +80,10 @@ static void penalty_lookup(struct penalty_context *ctx)
 			penalty_print_line(ctx, &penalty_line);
 		} T_END;
 	}
-	if (input->stream_errno != 0)
-		i_fatal("read(%s) failed: %m", ctx->anvil_path);
+	if (input->stream_errno != 0) {
+		i_fatal("read(%s) failed: %s", ctx->anvil_path,
+			i_stream_get_error(input));
+	}
 
 	i_stream_destroy(&input);
 }
diff --git a/src/doveadm/doveadm-replicator.c b/src/doveadm/doveadm-replicator.c
index 6459a6c0f9..390572b530 100644
--- a/src/doveadm/doveadm-replicator.c
+++ b/src/doveadm/doveadm-replicator.c
@@ -48,9 +48,10 @@ static void replicator_connect(struct replicator_context *ctx)
 	line = i_stream_read_next_line(ctx->input);
 	alarm(0);
 	if (line == NULL) {
-		if (ctx->input->stream_errno != 0)
-			i_fatal("read(%s) failed: %m", ctx->socket_path);
-		else if (ctx->input->eof)
+		if (ctx->input->stream_errno != 0) {
+			i_fatal("read(%s) failed: %s", ctx->socket_path,
+				i_stream_get_error(ctx->input));
+		} else if (ctx->input->eof)
 			i_fatal("%s disconnected", ctx->socket_path);
 		else
 			i_fatal("read(%s) timed out", ctx->socket_path);
@@ -64,8 +65,10 @@ static void replicator_connect(struct replicator_context *ctx)
 
 static void replicator_disconnect(struct replicator_context *ctx)
 {
-	if (ctx->input->stream_errno != 0)
-		i_fatal("read(%s) failed: %m", ctx->socket_path);
+	if (ctx->input->stream_errno != 0) {
+		i_fatal("read(%s) failed: %s", ctx->socket_path,
+			i_stream_get_error(ctx->input));
+	}
 	i_stream_destroy(&ctx->input);
 }
 
diff --git a/src/doveadm/doveadm-stats.c b/src/doveadm/doveadm-stats.c
index 81e6f25623..54201ed78a 100644
--- a/src/doveadm/doveadm-stats.c
+++ b/src/doveadm/doveadm-stats.c
@@ -111,7 +111,7 @@ static void stats_dump(const char *path, const char *cmd)
 		} while (args != NULL);
 	}
 	if (input->stream_errno != 0)
-		i_fatal("read(%s) failed: %m", path);
+		i_fatal("read(%s) failed: %s", path, i_stream_get_error(input));
 	i_stream_destroy(&input);
 }
 
@@ -194,8 +194,10 @@ static void stats_read(struct top_context *ctx)
 		hash_table_insert(ctx->sessions, line->id, line);
 	}
 
-	if (ctx->input->stream_errno != 0)
-		i_fatal("read(%s) failed: %m", ctx->path);
+	if (ctx->input->stream_errno != 0) {
+		i_fatal("read(%s) failed: %s", ctx->path,
+			i_stream_get_error(ctx->input));
+	}
 	i_fatal("read(%s): unexpected EOF", ctx->path);
 }
 
diff --git a/src/doveadm/doveadm-who.c b/src/doveadm/doveadm-who.c
index 3b75b9a9a6..d0f3b0f5d7 100644
--- a/src/doveadm/doveadm-who.c
+++ b/src/doveadm/doveadm-who.c
@@ -169,8 +169,10 @@ void who_lookup(struct who_context *ctx, who_callback_t *callback)
 				callback(ctx, &who_line);
 		} T_END;
 	}
-	if (input->stream_errno != 0)
-		i_fatal("read(%s) failed: %m", ctx->anvil_path);
+	if (input->stream_errno != 0) {
+		i_fatal("read(%s) failed: %s", ctx->anvil_path,
+			i_stream_get_error(input));
+	}
 
 	i_stream_destroy(&input);
 }
diff --git a/src/doveadm/doveadm-zlib.c b/src/doveadm/doveadm-zlib.c
index 957d4dd42d..10c964afb9 100644
--- a/src/doveadm/doveadm-zlib.c
+++ b/src/doveadm/doveadm-zlib.c
@@ -122,8 +122,8 @@ static void server_input(struct client *client)
 
 	if (i_stream_read(client->input) == -1) {
 		if (client->input->stream_errno != 0) {
-			errno = client->input->stream_errno;
-			i_fatal("read(server) failed: %m");
+			i_fatal("read(server) failed: %s",
+				i_stream_get_error(client->input));
 		}
 
 		i_info("Server disconnected");
diff --git a/src/lib-auth/auth-master.c b/src/lib-auth/auth-master.c
index a138417e20..b3ceab510f 100644
--- a/src/lib-auth/auth-master.c
+++ b/src/lib-auth/auth-master.c
@@ -413,7 +413,8 @@ static int auth_master_run_cmd_pre(struct auth_master_connection *conn,
 	o_stream_uncork(conn->output);
 
 	if (o_stream_nfinish(conn->output) < 0) {
-		i_error("write(auth socket) failed: %m");
+		i_error("write(auth socket) failed: %s",
+			o_stream_get_error(conn->output));
 		auth_master_unset_io(conn);
 		auth_connection_close(conn);
 		return -1;
diff --git a/src/lib-auth/auth-server-connection.c b/src/lib-auth/auth-server-connection.c
index 528d49a671..8453a3a61f 100644
--- a/src/lib-auth/auth-server-connection.c
+++ b/src/lib-auth/auth-server-connection.c
@@ -453,9 +453,10 @@ int auth_server_connection_connect(struct auth_server_connection *conn)
                                     AUTH_CLIENT_PROTOCOL_MINOR_VERSION,
 				    conn->client->client_pid);
 	if (o_stream_send_str(conn->output, handshake) < 0) {
-		i_warning("Error sending handshake to auth server: %m");
+		i_warning("Error sending handshake to auth server: %s",
+			  o_stream_get_error(conn->output));
 		auth_server_connection_disconnect(conn,
-			strerror(conn->output->last_failed_errno));
+			o_stream_get_error(conn->output));
 		return -1;
 	}
 
diff --git a/src/lib-http/http-server-response.c b/src/lib-http/http-server-response.c
index f837936474..0c721d2f12 100644
--- a/src/lib-http/http-server-response.c
+++ b/src/lib-http/http-server-response.c
@@ -142,8 +142,8 @@ void http_server_response_set_payload(struct http_server_response *resp,
 	resp->payload_input = input;
 	if ((ret = i_stream_get_size(input, TRUE, &resp->payload_size)) <= 0) {
 		if (ret < 0) {
-			i_error("i_stream_get_size(%s) failed: %m",
-				i_stream_get_name(input));
+			i_error("i_stream_get_size(%s) failed: %s",
+				i_stream_get_name(input), i_stream_get_error(input));
 		}
 		resp->payload_size = 0;
 		resp->payload_chunked = TRUE;
@@ -500,16 +500,16 @@ int http_server_response_send_more(struct http_server_response *resp,
 	if (resp->payload_input->stream_errno != 0) {
 		/* we're in the middle of sending a response, so the connection
 		   will also have to be aborted */
-		errno = resp->payload_input->stream_errno;
-		*error_r = t_strdup_printf("read(%s) failed: %m",
-					   i_stream_get_name(resp->payload_input));
+		*error_r = t_strdup_printf("read(%s) failed: %s",
+			i_stream_get_name(resp->payload_input),
+			i_stream_get_error(resp->payload_input));
 		ret = -1;
 	} else if (output->stream_errno != 0) {
 		/* failed to send response */
-		errno = output->stream_errno;
-		if (errno != EPIPE && errno != ECONNRESET) {
-			*error_r = t_strdup_printf("write(%s) failed: %m",
-					   o_stream_get_name(output));
+		if (output->stream_errno != EPIPE &&
+		    output->stream_errno != ECONNRESET) {
+			*error_r = t_strdup_printf("write(%s) failed: %s",
+				o_stream_get_name(output), o_stream_get_error(output));
 		}
 		ret = -1;
 	} else {
@@ -646,9 +646,10 @@ static int http_server_response_send_real(struct http_server_response *resp,
 	o_stream_ref(output);
 	o_stream_cork(output);
 	if (o_stream_sendv(output, iov, N_ELEMENTS(iov)) < 0) {
-		if (errno != EPIPE && errno != ECONNRESET) {
-			*error_r = t_strdup_printf("write(%s) failed: %m",
-					   o_stream_get_name(output));
+		if (output->stream_errno != EPIPE &&
+		    output->stream_errno != ECONNRESET) {
+			*error_r = t_strdup_printf("write(%s) failed: %s",
+				o_stream_get_name(output), o_stream_get_error(output));
 		}
 		ret = -1;
 	}
diff --git a/src/lib-index/mail-index-strmap.c b/src/lib-index/mail-index-strmap.c
index 4f5de33d09..549eaf45f1 100644
--- a/src/lib-index/mail-index-strmap.c
+++ b/src/lib-index/mail-index-strmap.c
@@ -1017,8 +1017,8 @@ static int mail_index_strmap_recreate(struct mail_index_strmap_view *view)
 	o_stream_cork(output);
 	mail_index_strmap_recreate_write(view, output);
 	if (o_stream_nfinish(output) < 0) {
-		mail_index_set_error(strmap->index,
-				     "write(%s) failed: %m", temp_path);
+		mail_index_set_error(strmap->index, "write(%s) failed: %s",
+				     temp_path, o_stream_get_error(output));
 		ret = -1;
 	}
 	o_stream_destroy(&output);
diff --git a/src/lib-lda/duplicate.c b/src/lib-lda/duplicate.c
index 0e458d06ae..9cf1757325 100644
--- a/src/lib-lda/duplicate.c
+++ b/src/lib-lda/duplicate.c
@@ -317,7 +317,8 @@ void duplicate_flush(struct duplicate_context *ctx)
 	hash_table_iterate_deinit(&iter);
 
 	if (o_stream_nfinish(output) < 0) {
-		i_error("write(%s) failed: %m", file->path);
+		i_error("write(%s) failed: %s", file->path,
+			o_stream_get_error(output));
 		o_stream_unref(&output);
 		duplicate_file_free(&ctx->file);
 		return;
diff --git a/src/lib-lda/lmtp-client.c b/src/lib-lda/lmtp-client.c
index 5c91e7d72c..4d16a4ea12 100644
--- a/src/lib-lda/lmtp-client.c
+++ b/src/lib-lda/lmtp-client.c
@@ -603,8 +603,8 @@ static void lmtp_client_input(struct lmtp_client *client)
 		lmtp_client_fail(client,
 				 "501 5.5.4 Command reply line too long");
 	} else if (client->input->stream_errno != 0) {
-		errno = client->input->stream_errno;
-		i_error("lmtp client: read() failed: %m");
+		i_error("lmtp client: read() failed: %s",
+			i_stream_get_error(client->input));
 		lmtp_client_fail(client, ERRSTR_TEMP_REMOTE_FAILURE
 				 " (read failure)");
 	} else if (client->input->eof) {
diff --git a/src/lib-lda/smtp-client.c b/src/lib-lda/smtp-client.c
index 28bb1eb3b2..131766ef03 100644
--- a/src/lib-lda/smtp-client.c
+++ b/src/lib-lda/smtp-client.c
@@ -265,14 +265,14 @@ smtp_client_send_flush(struct smtp_client *smtp_client,
 	}
 
 	if (o_stream_nfinish(smtp_client->output) < 0) {
-		*error_r = t_strdup_printf("write(%s) failed: %m",
-					   smtp_client->temp_path);
+		*error_r = t_strdup_printf("write(%s) failed: %s",
+			smtp_client->temp_path, o_stream_get_error(smtp_client->output));
 		return -1;
 	}
 
 	if (o_stream_seek(smtp_client->output, 0) < 0) {
-		*error_r = t_strdup_printf("lseek(%s) failed: %m",
-					   smtp_client->temp_path);
+		*error_r = t_strdup_printf("lseek(%s) failed: %s",
+			smtp_client->temp_path, o_stream_get_error(smtp_client->output));
 		return -1;
 	}
 
diff --git a/src/lib-master/anvil-client.c b/src/lib-master/anvil-client.c
index 553b21b041..eff41ff578 100644
--- a/src/lib-master/anvil-client.c
+++ b/src/lib-master/anvil-client.c
@@ -113,7 +113,8 @@ static void anvil_input(struct anvil_client *client)
 		aqueue_delete_tail(client->queries);
 	}
 	if (client->input->stream_errno != 0) {
-		i_error("read(%s) failed: %m", client->path);
+		i_error("read(%s) failed: %s", client->path,
+			i_stream_get_error(client->input));
 		anvil_reconnect(client);
 	} else if (client->input->eof) {
 		i_error("read(%s) failed: EOF", client->path);
diff --git a/src/lib-master/master-instance.c b/src/lib-master/master-instance.c
index b05ecb2900..271adfe278 100644
--- a/src/lib-master/master-instance.c
+++ b/src/lib-master/master-instance.c
@@ -116,7 +116,7 @@ static int master_instance_list_refresh(struct master_instance_list *list)
 			i_error("Invalid line in %s: %s", list->path, line);
 	} T_END;
 	if (input->stream_errno != 0) {
-		i_error("read(%s) failed: %m", line);
+		i_error("read(%s) failed: %s", line, i_stream_get_error(input));
 		ret = -1;
 	}
 	i_stream_destroy(&input);
@@ -147,7 +147,7 @@ master_instance_list_write(struct master_instance_list *list,
 		o_stream_nsend(output, str_data(str), str_len(str));
 	}
 	if (o_stream_nfinish(output) < 0) {
-		i_error("write(%s) failed: %m", path);
+		i_error("write(%s) failed: %s", path, o_stream_get_error(output));
 		ret = -1;
 	}
 	o_stream_destroy(&output);
diff --git a/src/lib-master/master-service-settings.c b/src/lib-master/master-service-settings.c
index 5d02c2b80b..4a25f6592c 100644
--- a/src/lib-master/master-service-settings.c
+++ b/src/lib-master/master-service-settings.c
@@ -327,7 +327,8 @@ config_read_reply_header(struct istream *istream, const char *path, pool_t pool,
 		if (ret == 0)
 			return 1;
 		*error_r = istream->stream_errno != 0 ?
-			t_strdup_printf("read(%s) failed: %m", path) :
+			t_strdup_printf("read(%s) failed: %s", path,
+					i_stream_get_error(istream)) :
 			t_strdup_printf("read(%s) failed: EOF", path);
 		return -1;
 	}
diff --git a/src/lib-storage/index/cydir/cydir-save.c b/src/lib-storage/index/cydir/cydir-save.c
index 0131521ef0..f2a7e9b4d9 100644
--- a/src/lib-storage/index/cydir/cydir-save.c
+++ b/src/lib-storage/index/cydir/cydir-save.c
@@ -151,7 +151,8 @@ static int cydir_save_flush(struct cydir_save_context *ctx, const char *path)
 	int ret = 0;
 
 	if (o_stream_nfinish(ctx->ctx.data.output) < 0) {
-		mail_storage_set_critical(storage, "write(%s) failed: %m", path);
+		mail_storage_set_critical(storage, "write(%s) failed: %s", path,
+			o_stream_get_error(ctx->ctx.data.output));
 		ret = -1;
 	}
 
diff --git a/src/lib-storage/index/dbox-multi/mdbox-purge.c b/src/lib-storage/index/dbox-multi/mdbox-purge.c
index a8911412cc..fc566a8430 100644
--- a/src/lib-storage/index/dbox-multi/mdbox-purge.c
+++ b/src/lib-storage/index/dbox-multi/mdbox-purge.c
@@ -78,7 +78,8 @@ mdbox_file_read_metadata_hdr(struct dbox_file *file,
 			return 0;
 		}
 		mail_storage_set_critical(&file->storage->storage,
-			"read(%s) failed: %m", file->cur_path);
+			"read(%s) failed: %s", file->cur_path,
+			i_stream_get_error(file->input));
 		return -1;
 	}
 
@@ -191,7 +192,6 @@ mdbox_purge_save_msg(struct mdbox_purge_context *ctx, struct dbox_file *file,
 	enum mdbox_map_append_flags append_flags;
 	uoff_t msg_size;
 	off_t ret;
-	int read_errno;
 
 	if (ctx->append_ctx == NULL)
 		ctx->append_ctx = mdbox_map_append_begin(ctx->atomic);
@@ -207,19 +207,19 @@ mdbox_purge_save_msg(struct mdbox_purge_context *ctx, struct dbox_file *file,
 
 	input = i_stream_create_limit(file->input, msg_size);
 	ret = o_stream_send_istream(output, input);
-	read_errno = input->stream_errno;
-	i_stream_unref(&input);
-
-	if (read_errno != 0) {
-		errno = read_errno;
+	if (input->stream_errno != 0) {
 		mail_storage_set_critical(&file->storage->storage,
-			"read(%s) failed: %m", file->cur_path);
+			"read(%s) failed: %s", file->cur_path,
+			i_stream_get_error(input));
+		i_stream_unref(&input);
 		return -1;
 	}
+	i_stream_unref(&input);
 	if (o_stream_nfinish(output) < 0) {
 		mail_storage_set_critical(&file->storage->storage,
-					  "write(%s) failed: %m",
-					  out_file_append->file->cur_path);
+					  "write(%s) failed: %s",
+					  out_file_append->file->cur_path,
+					  o_stream_get_error(output));
 		return -1;
 	}
 	if (ret != (off_t)msg_size) {
diff --git a/src/lib-storage/index/dbox-single/sdbox-file.c b/src/lib-storage/index/dbox-single/sdbox-file.c
index 4cdaaf2aa7..47622b9fed 100644
--- a/src/lib-storage/index/dbox-single/sdbox-file.c
+++ b/src/lib-storage/index/dbox-single/sdbox-file.c
@@ -323,20 +323,15 @@ int sdbox_file_move(struct dbox_file *file, bool alt_path)
 
 	output = o_stream_create_fd_file(out_fd, 0, FALSE);
 	i_stream_seek(file->input, 0);
-	while ((ret = o_stream_send_istream(output, file->input)) > 0) ;
+	ret = o_stream_send_istream(output, file->input) > 0 ? 0 : -1;
 	if (o_stream_nfinish(output) < 0) {
-		mail_storage_set_critical(storage, "write(%s) failed: %m",
-					  temp_path);
+		mail_storage_set_critical(storage, "write(%s) failed: %s",
+			temp_path, o_stream_get_error(output));
 		ret = -1;
 	} else if (file->input->stream_errno != 0) {
-		errno = file->input->stream_errno;
-		dbox_file_set_syscall_error(file, "ftruncate()");
+		mail_storage_set_critical(storage, "read(%s) failed: %s",
+			temp_path, i_stream_get_error(file->input));
 		ret = -1;
-	} else if (ret < 0) {
-		mail_storage_set_critical(storage,
-			"o_stream_send_istream(%s, %s) "
-			"failed with unknown error",
-			temp_path, file->cur_path);
 	}
 	o_stream_unref(&output);
 
diff --git a/src/lib-storage/index/imapc/imapc-save.c b/src/lib-storage/index/imapc/imapc-save.c
index ff9e23b228..b8a6919b5f 100644
--- a/src/lib-storage/index/imapc/imapc-save.c
+++ b/src/lib-storage/index/imapc/imapc-save.c
@@ -274,7 +274,8 @@ int imapc_save_finish(struct mail_save_context *_ctx)
 		if (o_stream_nfinish(_ctx->data.output) < 0) {
 			if (!mail_storage_set_error_from_errno(storage)) {
 				mail_storage_set_critical(storage,
-					"write(%s) failed: %m", ctx->temp_path);
+					"write(%s) failed: %s", ctx->temp_path,
+					o_stream_get_error(_ctx->data.output));
 			}
 			ctx->failed = TRUE;
 		}
diff --git a/src/lib-storage/index/index-attachment.c b/src/lib-storage/index/index-attachment.c
index 5ec3efd042..4b7abd9129 100644
--- a/src/lib-storage/index/index-attachment.c
+++ b/src/lib-storage/index/index-attachment.c
@@ -196,10 +196,9 @@ static int save_check_write_error(struct mail_storage *storage,
 	if (output->last_failed_errno == 0)
 		return 0;
 
-	errno = output->last_failed_errno;
 	if (!mail_storage_set_error_from_errno(storage)) {
-		mail_storage_set_critical(storage, "write(%s) failed: %m",
-					  o_stream_get_name(output));
+		mail_storage_set_critical(storage, "write(%s) failed: %s",
+			o_stream_get_name(output), o_stream_get_error(output));
 	}
 	return -1;
 }
diff --git a/src/lib-storage/index/maildir/maildir-save.c b/src/lib-storage/index/maildir/maildir-save.c
index 8999737a9d..f20fd76afb 100644
--- a/src/lib-storage/index/maildir/maildir-save.c
+++ b/src/lib-storage/index/maildir/maildir-save.c
@@ -524,7 +524,7 @@ static int maildir_save_finish_real(struct mail_save_context *_ctx)
 {
 	struct maildir_save_context *ctx = (struct maildir_save_context *)_ctx;
 	struct mail_storage *storage = &ctx->mbox->storage->storage;
-	const char *path;
+	const char *path, *output_errstr;
 	off_t real_size;
 	uoff_t size;
 	int output_errno;
@@ -539,7 +539,8 @@ static int maildir_save_finish_real(struct mail_save_context *_ctx)
 	if (!ctx->failed && o_stream_nfinish(_ctx->data.output) < 0) {
 		if (!mail_storage_set_error_from_errno(storage)) {
 			mail_storage_set_critical(storage,
-				"write(%s) failed: %m", path);
+				"write(%s) failed: %s", path,
+				o_stream_get_error(_ctx->data.output));
 		}
 		ctx->failed = TRUE;
 	}
@@ -570,6 +571,7 @@ static int maildir_save_finish_real(struct mail_save_context *_ctx)
 		ctx->file_last->vsize = (uoff_t)-1;
 
 	output_errno = _ctx->data.output->last_failed_errno;
+	output_errstr = t_strdup(o_stream_get_error(_ctx->data.output));
 	o_stream_destroy(&_ctx->data.output);
 
 	if (storage->set->parsed_fsync_mode != FSYNC_MODE_NEVER &&
@@ -613,13 +615,12 @@ static int maildir_save_finish_real(struct mail_save_context *_ctx)
 		/* delete the tmp file */
 		i_unlink_if_exists(path);
 
-		errno = output_errno;
-		if (ENOQUOTA(errno)) {
+		if (ENOQUOTA(output_errno)) {
 			mail_storage_set_error(storage,
 				MAIL_ERROR_NOQUOTA, MAIL_ERRSTR_NO_QUOTA);
-		} else if (errno != 0) {
+		} else if (output_errno != 0) {
 			mail_storage_set_critical(storage,
-				"write(%s) failed: %m", path);
+				"write(%s) failed: %s", path, output_errstr);
 		}
 
 		maildir_save_remove_last_filename(ctx);
diff --git a/src/lib-storage/index/maildir/maildir-uidlist.c b/src/lib-storage/index/maildir/maildir-uidlist.c
index eb89aa558d..b0208f2672 100644
--- a/src/lib-storage/index/maildir/maildir-uidlist.c
+++ b/src/lib-storage/index/maildir/maildir-uidlist.c
@@ -832,9 +832,9 @@ maildir_uidlist_update_read(struct maildir_uidlist *uidlist,
                 if (input->stream_errno == ESTALE && try_retry)
 			*retry_r = TRUE;
 		else {
-			errno = input->stream_errno;
 			mail_storage_set_critical(storage,
-				"read(%s) failed: %m", uidlist->path);
+				"read(%s) failed: %s", uidlist->path,
+				i_stream_get_error(input));
 		}
 		uidlist->last_read_offset = 0;
 	}
@@ -1312,7 +1312,8 @@ static int maildir_uidlist_write_fd(struct maildir_uidlist *uidlist, int fd,
 	maildir_uidlist_iter_deinit(&iter);
 
 	if (o_stream_nfinish(output) < 0) {
-		mail_storage_set_critical(storage, "write(%s) failed: %m", path);
+		mail_storage_set_critical(storage, "write(%s) failed: %s", path,
+					  o_stream_get_error(output));
 		o_stream_unref(&output);
 		return -1;
 	}
diff --git a/src/lib/json-parser.c b/src/lib/json-parser.c
index fe54a19cdf..4e6afbf85c 100644
--- a/src/lib/json-parser.c
+++ b/src/lib/json-parser.c
@@ -133,8 +133,9 @@ int json_parser_deinit(struct json_parser **_parser, const char **error_r)
 		/* actual parser error */
 		*error_r = parser->error;
 	} else if (parser->input->stream_errno != 0) {
-		*error_r = t_strdup_printf("read(%s) failed: %m",
-					   i_stream_get_name(parser->input));
+		*error_r = t_strdup_printf("read(%s) failed: %s",
+					   i_stream_get_name(parser->input),
+					   i_stream_get_error(parser->input));
 	} else if (parser->data == parser->end &&
 		   !i_stream_have_bytes_left(parser->input) &&
 		   parser->state != JSON_STATE_DONE) {
diff --git a/src/plugins/acl/acl-backend-vfile-acllist.c b/src/plugins/acl/acl-backend-vfile-acllist.c
index 28764171b0..6e3fd226d9 100644
--- a/src/plugins/acl/acl-backend-vfile-acllist.c
+++ b/src/plugins/acl/acl-backend-vfile-acllist.c
@@ -279,7 +279,8 @@ acl_backend_vfile_acllist_try_rebuild(struct acl_backend_vfile *backend)
 	}
 
 	if (o_stream_nfinish(output) < 0) {
-		i_error("write(%s) failed: %m", str_c(path));
+		i_error("write(%s) failed: %s", str_c(path),
+			o_stream_get_error(output));
 		ret = -1;
 	}
 	if (mailbox_list_iter_deinit(&iter) < 0)
diff --git a/src/plugins/acl/acl-backend-vfile-update.c b/src/plugins/acl/acl-backend-vfile-update.c
index ecd2dea99d..0c2ebadee0 100644
--- a/src/plugins/acl/acl-backend-vfile-update.c
+++ b/src/plugins/acl/acl-backend-vfile-update.c
@@ -159,7 +159,8 @@ acl_backend_vfile_update_write(struct acl_object *aclobj,
 	}
 	str_free(&str);
 	if (o_stream_nfinish(output) < 0) {
-		i_error("write(%s) failed: %m", path);
+		i_error("write(%s) failed: %s", path,
+			o_stream_get_error(output));
 		ret = -1;
 	}
 	o_stream_destroy(&output);
diff --git a/src/plugins/acl/acl-backend-vfile.c b/src/plugins/acl/acl-backend-vfile.c
index 188a41cbaa..db8048a5df 100644
--- a/src/plugins/acl/acl-backend-vfile.c
+++ b/src/plugins/acl/acl-backend-vfile.c
@@ -393,7 +393,8 @@ acl_backend_vfile_read(struct acl_object *aclobj, bool global, const char *path,
 			ret = 0;
 		else {
 			ret = -1;
-			i_error("read(%s) failed: %m", path);
+			i_error("read(%s) failed: %s", path,
+				i_stream_get_error(input));
 		}
 	} else {
 		if (fstat(fd, &st) < 0) {
diff --git a/src/plugins/fts-squat/squat-trie.c b/src/plugins/fts-squat/squat-trie.c
index 0861f21b0c..b3d8fa301b 100644
--- a/src/plugins/fts-squat/squat-trie.c
+++ b/src/plugins/fts-squat/squat-trie.c
@@ -1680,7 +1680,8 @@ static int squat_trie_write(struct squat_trie_build_context *ctx)
 		o_stream_nsend(output, &trie->hdr, sizeof(trie->hdr));
 	}
 	if (o_stream_nfinish(output) < 0) {
-		i_error("write() to %s failed: %m", path);
+		i_error("write(%s) failed: %s", path,
+			o_stream_get_error(output));
 		ret = -1;
 	}
 	o_stream_destroy(&output);
diff --git a/src/plugins/fts-squat/squat-uidlist.c b/src/plugins/fts-squat/squat-uidlist.c
index 92bc86fa46..1b7fb1cad1 100644
--- a/src/plugins/fts-squat/squat-uidlist.c
+++ b/src/plugins/fts-squat/squat-uidlist.c
@@ -861,7 +861,8 @@ int squat_uidlist_build_finish(struct squat_uidlist_build_context *ctx)
 	}
 
 	if (o_stream_nfinish(ctx->output) < 0) {
-		i_error("write() to %s failed: %m", ctx->uidlist->path);
+		i_error("write() to %s failed: %s", ctx->uidlist->path,
+			o_stream_get_error(ctx->output));
 		return -1;
 	}
 	return 0;
@@ -1064,7 +1065,8 @@ int squat_uidlist_rebuild_finish(struct squat_uidlist_rebuild_context *ctx,
 		if (ctx->uidlist->corrupted)
 			ret = -1;
 		else if (o_stream_nfinish(ctx->output) < 0) {
-			i_error("write() to %s failed: %m", temp_path);
+			i_error("write(%s) failed: %s", temp_path,
+				o_stream_get_error(ctx->output));
 			ret = -1;
 		} else if (rename(temp_path, ctx->uidlist->path) < 0) {
 			i_error("rename(%s, %s) failed: %m",
diff --git a/src/plugins/fts/fts-expunge-log.c b/src/plugins/fts/fts-expunge-log.c
index cf94ba12bb..667d66ac7f 100644
--- a/src/plugins/fts/fts-expunge-log.c
+++ b/src/plugins/fts/fts-expunge-log.c
@@ -424,7 +424,8 @@ fts_expunge_log_read_failure(struct fts_expunge_log_read_ctx *ctx,
 
 	if (ctx->input->stream_errno != 0) {
 		ctx->failed = TRUE;
-		i_error("read(%s) failed: %m", ctx->log->path);
+		i_error("read(%s) failed: %s", ctx->log->path,
+			i_stream_get_error(ctx->input));
 	} else {
 		size = i_stream_get_data_size(ctx->input);
 		ctx->corrupted = TRUE;