Unable to send receive via IMAP

Unable to send receive via IMAP

Unable to send email from my Gapp address. 
Message CRM_ERROR_500::::::EXCEPTION

Mailed ZOHO 24 hours ago and other than the automated response, nothing!

Appreciate IMAP has presented numerous issues for ZOHO previously, but is really the only option for our business.

Any help would be gratefully received, especially if you know how to improve the response time from Support!

John Wright