I have a client that we are migrating from exchange 2013 on prem to office 365. They use the built-in administrator account for emailing for a number of groups and don't want to change that. The office 365 system is the mx so all emails flow through it for antispam reasons.
The administrator account is in an OU that is configured for AD sync but it does not show up in the list in office 365 although all the other names are there so I'm guessing either it can't be synced or I'll have to edit something about the account. Any email will get a bounce and at least part of that reason is it doesn't sync that account as far as I can see.
CO1NAM11FT028.mail.protection.outlook.com rejected your message to the following email addresses:<o:p></o:p>
administrator@mydomain.com
A communication failure occurred during the delivery of this message. Please try resending the message later. If the problem continues, contact your helpdesk.<o:p></o:p>
CO1NAM11FT028.mail.protection.outlook.com gave this error:
Recipient address rejected: Access denied [CO1NAM11FT028.eop-nam11.prod.protection.outlook.com]<o:p></o:p>