diff -up -r a/imap/pop3d.c b/imap/pop3d.c
--- a/imap/pop3d.c	2023-09-25 01:54:13.000000000 +0200
+++ b/imap/pop3d.c	2023-11-03 15:16:17.498529618 +0100
@@ -2051,8 +2051,10 @@ static int blat(int msgno, int lines)
 
     /* Protect against messages not ending in CRLF */
     if (buf[strlen(buf)-1] != '\n') prot_printf(popd_out, "\r\n");
+    prot_flush(popd_out);
 
     prot_printf(popd_out, ".\r\n");
+    prot_flush(popd_out);
 
     /* Reset inactivity timer in case we spend a long time
        pushing data to the client over a slow link. */