Exchange IMAP log: invalid command

Technical assistance
1

Zammad 3.5 on Centos 7 (3.5.0-1602165773.71bff28e.centos7)
Exchange 2013 CU23 on-premises.
IMAP with TLS

During IMAP4 troubleshooting (after CU update on Exchange) I noticed this error in IMAP log file on Exchange server:
2020-10-14T17:42:39.040Z,0000000000000044,4,[fe80::bd7b:b28e:600e:26bd%20]:9933,[fe80::bd7b:b28e:600e:26bd%20]:40776,helpdesk,1,33,32,InvalidCommand,RUBY0003 SORT (DATE) US-ASCII ALL,“R=”“RUBY0003 BAD Command Error. 12"”;Budget="“Owner:Sid~BELAM\helpdesk~Imap~false,Conn:1,MaxConn:Unlimited,MaxBurst:3600000,Balance:3599998,Cutoff:Unlimited,RechargeRate:600000,Policy:GlobalThrottlingPolicy_012e855f-9c44-4645-b38c-4ef69152c032,IsServiceAccount:False,LiveTime:00:02:02.8769368"”"

Zammad works ok, it received mail from Exchange, no problem.
Do I need to worry about his error, can you fix it?

2

Do you happen to know which command Exchange complains about?

3

i was thinking, it is in the provided log:
SORT (DATE) US-ASCII ALL

4

Odd.
Especially if this error appears after an CU upgrade, things may have changed in your system itself.

The lines in question responsible for above are these:

They’re only relevant if you keep your messages on the server:

So, technically, if everything is fine and working, I’d say you could ignore this error.
Maybe check for the mailbox size.

Sometimes mail servers don’t like too big folders.
I’ve seen installations running in timeouts or even the mail server process crashing because of that.

5

I do not know, if this error was before CU update. I was trying to say, what after CU update, IMAP service on Exchange became disabled, I start loooking for possible reason, and noticed this error in log. But before update and after, Zammad works fine. I’m quite sure, what messages are not kept in mailbox, this is default mode, right?

6

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