User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; GTB7.1; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C) Steps to reproduce: compose a mail and send. SMTP server replies with code 550. Actual results: Thunderbird put the message into sent folder. Expected results: it should be go to draft folder, since: - previous versions put it into draft folder - there is no way to know whether thunderbird succeed or fail to send

550 in SMTP is following. > EHLO 550 Not implemented > RCPT,EXPN,VRFY 550 Requested action not taken: mailbox unavailable > http://www.greenend.org.uk/rjk/tech/smtpreplies.html#DATA 550 doesn't look defined for DATA. At which step was the 550 returned? (1) Tb -> (DATA command etc. by Tb) -> SMTP server (2) SMTP server -> Destination server (also SMTP server, front end of POP3, IMAP, Web Mail server) If "550 Requested action not taken: mailbox unavailable" from Destination server to SMTP server at step (2), it means that 250 is returned from SMTP server to Tb at step (1), and mail client like Tb can do nothing once mail data is successfully pased to SMTP server.

Problem was reproduced in bug 780124 and reply code was not relevant, so closing as DUP. If different problem, re-open this bug, please.

the case go through protocols like: S: 220 xxx.xxx.xxx.xxx.xxx ESMTP Postfix C: EHLO [xxx.xxx.xxx.xxx] S: 250-xxxx.xxxx.xxxx.xxxx | 250-SIZE 10000000 | 250-VRFY .... C: MAIL FROM:<xxxx.xxxx@xxx.xxxx> SIZE=xxx S: 250 2.1.0 ok C: RCPT TO:<xxxx@xxxx.xxxx> S: 250 2.1.5 ok C: DATA S: 354 Enter mail, end with "." on a line by itself (message iself) S: 550 5.1.1 xxxxxxxx Send Cancel the result seems the same as 780124 (put it into sent folder).