Created attachment 8510862 [details] IMAP log for mail.ru account I have this issue only with my mail.ru account. 1. Reply to your own message in the Sent folder. 2. Result - no "answered" arrow in the messages list, no "store (\Answered)" in the IMAP log. Replying from INBOX works fine. TB DOES set \Answered flag in Sent folder if I use my gmx account. The servers have some differences in capabilities mail.ru: IMAP4rev1 ID XLIST UIDPLUS UNSELECT MOVE AUTH=PLAIN AUTH=XOAUTH2 gmx.com: IMAP4rev1 CHILDREN ENABLE ID IDLE LIST-EXTENDED LIST-STATUS LITERAL+ MOVE NAMESPACE SASL-IR SORT SPECIAL-USE THREAD=ORDEREDSUBJECT UIDPLUS UNSELECT WITHIN AUTH=LOGIN AUTH=PLAIN And actual name for mail.ru's Sent folder is "Отправленные" (in Russian) and it's stored on disk in a fancy named file &BB4EQgQ,BEAEMAQyBDsENQQ9BD0ESwQ1-. I can create mail.ru acc for testing for you if you wish. mozillazine topic http://forums.mozillazine.org/viewtopic.php?f=39&t=2882339
Some more info. For testing I created two folders TEST and ТЕСТ (in Russian). Replying from both works fine, \Answered was sent.
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