That “U=xxx” is the IMAP UID, which is a unique identifier that message has in the IMAP mailbox. mbsync adds that to the filename just so it can track which (local) message corresponds to what message on the IMAP server.
When moving a message from one mailbox (folder) to another, this UID changes, because it’s per-mailbox only. If you read the manpage for mbsync, it says explicitly that the MUA should strip the U=xxx when moving between maildirs, so the behavior of aerc here is correct.
In order to get to the bottom of this, you’d probably have to enable the debug output of mbsync and look at exactly what IMAP commands it sends to Gmail, then decipher the relevant command(s) by looking at the RFC, and then decide whether it’s Gmail or mbsync’s fault this gets lost. You could also contact the mbsync devs with this I guess.
I found someone complaining about the same issue, without getting a reply, 7 years ago, except that person was using mutt: https://stackoverflow.com/questions/52218254/isync-mbsync-on-gmail-marks-mail-as-new-after-move-to-another-folder
That doesn’t help you obviously but from this we might guess it’s probably not aerc’s fault.















Und schriftliche Polynomdivision sollte man wissen weil?
Ich glaube wenn man allgemein algebraisches Verständnis hat und grundsätzlich irgendwie dividieren kann, kann man auch recht schnell lernen Polynome zu dividieren, ohne den Algorithmus auswendig gelernt zu haben.
Mal abgesehen davon, wieso Polynomdivision überhaupt mehr oder weniger relevant sein sollte als andere Sachen, die momentan nicht im Lehrplan sind.