What do you see in sogo logs ? Is there multiple calls to caldav urls ?

Same issue encountered here (debian 11 with iRedMail Easy configuration)

Postfix shows every 5 minutes a SOGo connexion followed by an automated invitation reply message.
This happens on business hours only, when the SOGo web interface is opened in the browser of the user whose accounts send the repeated replies.

In the SOGo logs:

Jan 10 11:56:37 sogod [2199457]: <0x0x55f3e2f6e560[GCSFolder]> ERROR(-[GCSFolder writeContent:fromComponen
t:container:toName:baseVersion:]): cannot insert content : <MySQL4Exception: 0x55f3dd059860> NAME:Executio
nFailed REASON:Incorrect string value: '\xF0\x9F\x98\x89)\x0A...' for column sogo.sogo_quick_appointmen t.c_description at row 1
Jan 10 11:56:37 sogod [2199457]: [ERROR] <0x55f3ea1fb7e0[SOGoAppointmentObject]:040000008200E00074C5B7101A
82E00800000000009B4D0F7F5BDB0100000000000000001000000065696F7A7D038C409AA5FE5F38D73CFB.ics> write failed:
<MySQL4Exception: 0x55f3dd059860> NAME:ExecutionFailed REASON:Incorrect string value: '\xF0\x9F\x98\x89)\x
0A...' for column sogo.sogo_quick_appointment.c_description at row 1

Those errors always seem to happen 1 or 2 seconds before the mail pops in postfix.

The event invitation which caused this has been generated by Microsoft Teams, and thus is very long and contains emojis (an entire email thread is embedded in the event description)

This could be related to this other issue about SOGo database charset and encoding: https://bugs.sogo.nu/view.php?id=5630#c16393

If I try to guess the chain of events :

1. an email containing an invitation is received
2. the user accepts it
3. SOGo tries to save the event but fails
4. a reply email is sent regardless
5. 5 minutes after, SOGo tries again: GOTO 3.

And this for the entire lifetime of the web tab — the problem pauses while the computer sleeps, stops only if the tab is closed or refreshed.