Issue symptoms
When my customers email us, they receive a mailer-daemon from Google. This email announces that the support address couldn't be found. Additionally, it includes a response with the message the account [user's email] is disabled.
Resolution steps
This can happen if your external support email address is a Google Group. Instruct the customer to sign in to Google with the affected email address, then start the appeal process.
Review this Google article: Ask us to restore your account. The customer may not be able to appeal on that page. If that happens, contact Google support for assistance. For more information, see How do I use Google Groups as a support address?
Warning: Zendesk does not support or guarantee that this method works correctly, nor can Zendesk troubleshoot issues caused by the use of Google Groups, email aliases, or similar methods. Zendesk does not block these methods. Use them at your own risk.