diff --git a/src/submission/submission-client.c b/src/submission/submission-client.c
index f98a16f436..be5156e2c1 100644
--- a/src/submission/submission-client.c
+++ b/src/submission/submission-client.c
@@ -207,6 +207,7 @@ struct client *client_create(int fd_in, int fd_out,
 	smtp_set.login_greeting = set->login_greeting;
 	smtp_set.max_recipients = set->submission_max_recipients;
 	smtp_set.max_client_idle_time_msecs = CLIENT_IDLE_TIMEOUT_MSECS;
+	smtp_set.max_message_size = set->submission_max_mail_size;
 	smtp_set.debug = user->mail_debug;
 
 	if ((workarounds & WORKAROUND_WHITESPACE_BEFORE_PATH) != 0) {
diff --git a/src/submission/submission-settings.c b/src/submission/submission-settings.c
index 29bce42ddc..35a82d04a5 100644
--- a/src/submission/submission-settings.c
+++ b/src/submission/submission-settings.c
@@ -100,7 +100,7 @@ static const struct submission_settings submission_default_settings = {
 	.login_greeting = PACKAGE_NAME" ready.",
 	.login_trusted_networks = "",
 
-	.submission_max_mail_size = 0,
+	.submission_max_mail_size = 40*1024*1024,
 	.submission_max_recipients = 0,
 	.submission_client_workarounds = "",
 	.submission_logout_format = "in=%i out=%o",