I'm using opensource mail server hmailserver and Claws Mail client connected via IMAP. In case I do not use SSL / TLS, I encounter the following bug: When I try to send a letter larger than ~10 kilobytes (no matter, with an attachment or just with a long text), Claws Mail gives me the following message: Error: Could not queue message for sending. Claws-Mail Network Log: * Account 'accountname': Connecting to IMAP server: server.name:143... [12:13:10] IMAP< * OK IMAPrev1 * IMAP connection is un-authenticated [12:13:11] IMAP> 1 CAPABILITY [12:13:11] IMAP< * CAPABILITY IMAP4 IMAP4rev1 CHILDREN IDLE QUOTA SORT ACL NAMESPACE RIGHTS=texk [12:13:11] IMAP< 1 OK CAPABILITY completed [12:13:11] IMAP> Logging accountname@domain.name to server.name using plaintext [12:13:11] IMAP< LOGIN completed [12:13:11] IMAP< Login to server.name successful [12:13:11] IMAP> 3 LIST "" "" [12:13:11] IMAP< * LIST (\Noselect) "\\" "" [12:13:11] IMAP< 3 OK LIST completed [12:13:11] IMAP> 4 SELECT Queue [12:13:11] IMAP< * 0 EXISTS [12:13:11] IMAP< * 0 RECENT [12:13:11] IMAP< * FLAGS (\Deleted \Seen \Draft \Answered \Flagged) [12:13:11] IMAP< * OK [UIDVALIDITY 1489512006] current uidvalidity [12:13:11] IMAP< * OK [UIDNEXT 16] next uid [12:13:11] IMAP< * OK [PERMANENTFLAGS (\Deleted \Seen \Draft \Answered \Flagged)] limited [12:13:11] IMAP< 4 OK [READ-WRITE] SELECT completed [12:13:11] IMAP- [fetching UIDs...] [12:13:11] IMAP> 5 UID FETCH 1:* (UID) [12:13:11] IMAP< 5 OK UID completed [12:13:11] IMAP> 6 APPEND Queue (\Seen) {29003} [12:13:11] IMAP< + Ready for literal data [12:13:11] IMAP> [data - 8166 bytes] [12:13:11] IMAP> [data - 8190 bytes] [12:13:11] IMAP> [data - 8190 bytes] ** IMAP error on server.name: stream error ** IMAP connection broken hMailServer log: "DEBUG" 3060 "2017-04-04 12:21:45.733" "The read operation failed. Bytes transferred: 0 Remote IP: ip_address, Session: 252, Code: 2, Message: End of file" "DEBUG" 3060 "2017-04-04 12:21:45.733" "Ending session 252" When I try to save a message as a draft, Claws Mail gives me the following message: Error: could not save draft. Network Log: [12:23:03] IMAP> 6 APPEND Drafts (\Seen) {28938} [12:23:03] IMAP< + Ready for literal data [12:23:03] IMAP> [data - 8179 bytes] [12:23:03] IMAP> [data - 8190 bytes] [12:23:03] IMAP> [data - 8190 bytes] ** IMAP error on server.name: stream error ** IMAP connection broken BUT! If I use SSL/TLS connection, the message is sent or saved as a draft without errors.
*** This bug has been marked as a duplicate of bug 2262 ***