Lately, I have had a few of my users getting bounce back messages with the following message:
mx.google.com #550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1 https://support.google.com/mail/answer/6596
vc5si4454764vdc.14 - gsmtp ##
We are running Exchange Server 2007 with an Outlook 2007 client.
On one of my users Outlook client, I created a new Outlook Profile and the problem seems to have stopped. But, I have 3 other users having the same issue.