How can I resolve problems with my external mailbox due to a PASS/QUIT command error?

Environment:

Non hosted mailboxes on the outlook.office365.com mail servers, all pods, all versions.

Resolution:

This answer applies when seeing failures in techmail with PASS or QUIT command not working properly on office365 mail servers with an error message: "-ERR Server Unavailable. 21". 

In the past, this issue was the result of a server load on the mailbox provider side which is out of our control. If your site is experiencing this problem please work with your mail provider, Outlook365, to fix this issue.

As an alternative to using external mailboxes, you may use mailboxes hosted on our infrastructure.  In fact, most contracts already include hosted mailboxes.  You will need to contact your Sales Account Manager for the number of Oracle-hosted mailboxes your organization is currently licensed for.  In order to create new mailboxes submit a service request with Technical Support.