Created attachment 138983 [details] akonadiconsole log file SUMMARY I use Kmail together with the `Enable Undo Send` option. For months, I have been suffering a seemingly random issue where some of my email replies randomly disappear into a black hole after the grace period. STEPS TO REPRODUCE 1. Enable the Undo Send option 2. Reply to an existing email EXPECTED RESULT - After a defined duration, your email should send out - The email sent out will be copied to the Sent folder - The intended recipient receives that email OBSERVED RESULT - I get a KDE notification saying my reply has been sent - The reply is removed from the Outbox - The IMAP server doesn't receive anything related to that email reply. A connection simply appears to be opened and closed. - The reply is never copied into the Sent folder - The intended recipient never receives the email reply The issue seemed to be random at first but I have now narrowed down the common characteristics of email replies that suffer from this issue. - This issue only occurs with the `Enable Undo Send` option - This issue only affects a limited number of addresses & threads - All of them are on private domains (not gmail, yahoo, protonmail, etc.) - This issue NEVER occurs when I send a NEW email; only with replies - If I BCC another address that doesn't suffer from that issue, the said address alone will receive the email. In the mail server logs, it appears as if I was replying to this said address alone (TO address doesn't show in the logs). In the Sent folder, the headers look normal (2 recipients). I ran `akonadiconsole` to try to identify the culprit. Please see the log file enclosed. I noticed the two following outputs: [2021-06-03T16:08:56.450Z] akonadi_sendlater_agent org.kde.pim.messagecore Error in address splitting: parseAddressList returned false! [2021-06-03T16:08:56.490Z] akonadi_sendlater_agent org.kde.pim.messagecomposer QueueJob failed with error "Message has no recipients." The issue is even more annoying that it: - fails silently - any trace of the reply you type disappears so you have to re-write that email; at the very least it should remain in the Outbox SOFTWARE/OS VERSIONS Kmail: 5.17.1 (21.04.1) Linux: Arch Linux, Kernel 5.12.8 KDE Plasma Version: 5.21.5 KDE Frameworks Version: 5.82.0 Qt Version: 5.12.2