Hi - I've been having some issues with addresses at a particular domain recently where I keep getting the following undelivered address:
Your message did not reach some or all of the intended recipients.
Subject: FW: MS Teams permissions
Sent: 11/09/2020 13:19
The following recipient(s) cannot be reached:
'XXXX' on 11/09/2020 13:20
Server error: '550 5.1.2 Recipient Domain Invalid (VM521)'
Thing is, I don't get the message consistently - some go through to a person one minute and not the next. Also, if I use auto-complete they don't go through 99% if the time (but sometimes they do and yes, I've checked for typos millions of times) but if I type the very same address as auto-complete they mostly go through, but not every time. Similarly, replying to an email will sometimes go through and sometimes not. This varies a few times in the course of a day and is incredibly frustrating! Any ideas what I can do?