Version: (using KDE 3.5.10) OS: Linux Installed from: Ubuntu Packages Sending an email just failed with some server side issues. Kmail opened a pop-up stating: Sending failed: Unknown error code 50 The message content was not accepted. The server responded: "4.7.0 Temporary System Problem. Try again later (). 25sm10856572mul.29" This is a temporary failure. You may try again later. Please send a full bug report at http://bugs.kde.org. The message will stay in the 'outbox' folder until you either fix the problem (e.g. a broken address) or remove the message from the 'outbox' folder. It seems to have identified the temporary failure, but still pops up the unknown error and asks to report, which is what I did.
*** This bug has been marked as a duplicate of bug 146179 ***