Email to Issue not working from Zendesk

I use the issue mail adress to generated issues in my GitLab Issue page from Zendesk.
But for some reason it does not work anymore.
If I send a issue from my Ticket System Zendesk to the issue mail adress it does not generate an issue.

So is there any log or how can I solve this problem?
It has worked before and stopped working since a few days.

It is working if I manually send a mail to the issue mail address form my private mail account.
So it seems it is not a general problem, but does not work with the automated Zendesk Mail.

Any tips?

I have seen I got a response back.

“Unfortunately, your email message to GitLab could not be processed. We couldn’t figure out what user corresponds to the email. Please create your comment through the web interface.”

What does this mean?
The “from” address is a user in GitLab.

Problem solved.

My Zendesk Account send the mail from a different mail address/domain.
Gitlab checks now the mail address/domain and cannot connect the “issue mail address” with the account.
Becuase the issue mail address is from the main account/domain.

I have created a new GitLab user with the mail address/domain of the Zendesk Account.
I added this new user to my project as member on the main account.
IMPORTANT: You need to use the issue mail address from the new created user (not the main account).
Now all is working fine again.

Gitlab check the issue mail with the “from” mail/domain and find the connection and the correct user.
Because the new user has access to the main project in the main account a new issue will be created from this user.