submissiond xoauth2 authentication: line too long

[Tobias Florek]

Hi,

I am running the latest container image which has
  dovecot-submissiond    2:2.3.20-3+debian11

I am running into the following problem.  I have successfully set up 
xoauth2 for IMAP and ManageSieve.

Now when roundcube tries to send email to submissiond it fails with
  500 5.5.2 Line too long

This happens right after roundcube sends
  AUTH XOAUTH2 dXNlcj10ZkBzY2hhZWZmZXItYWcu[...]
(a line of length 2149 characters).

Reading RFC 4954, section 4 I suppose that this does not look standard 
compliant.  Am I correct?  I will raise this issue with roundcube as well.

Cheers,
  Tobi