dovecot: quota-status: Error: quota-status: Client sent invalid recipient address: Invalid character

The message in the subject has suddenly appeared in our mail.log over the last two days and we cannot pinpoint it down to anything specific. No changes or updates have been made to the system.
There is also nothing preceding the log entries which appears like an invalid email address.
Ubuntu is running at 20.04.4 LTS (GNU/Linux 5.4.0-121-generic x86_64)
ISPConfig version is 3.2.5 and dovecot is at version 2.3.7.2 (3c910f64b)
Please advise.

 

My gueess is it it an e-mail arriving at your system that causes that entry to log. You might figure out which email by comparing mail log timestamps to that log entry timestamp.
Seems this issue is known (found this using Internet Search engines with the error message you posted): https://www.mail-archive.com/[email protected]/msg74833.html

 

Thanks for your reply! I have already found the issue you have kindly posted and this does not seem to apply to the recipient addresses which cause the error. (none of the addresses contain double-quotes). For example, we have RUA reports sent from Google to dmarc @ ourdomain.com. These arrive almost on a daily basis, but sometimes this e-mail address triggers the quota-status error, sometimes it doesn't. I cannot nail it down to anything specific. Before the 27th June we have never received this error.

The article mentions patching dovecot, to get a more detailed error message, which seems prudent, but I don't think is a good idea, as dovecot is packaged with ISPConfig. Can you tell me if this patch is applied in dovecot in ISPConfig 3.2.8? Then I would perform an update and see if that either resolves the issue or at least offers more information.

 

Dovecot is not packaged with ISPCOnfig.
My understanding is the patch would not fix the issue, merely provide more detailed log info.
You have of verified the quota is not full?