When I try to send mail from outlook 2016 desktop, I get this message since the beginning of this month. Once in a while, the mail is sent, but more often Outlook tries to relay through my (wholly unrelated) private outlook account. Microsoft is no help at all. Do you have any idea what could be wrong?
Your message did not reach some or all of the intended recipients.
Subject: .....
Sent: 15-May-17 14:09
The following recipient(s) cannot be reached:
'recipient name' on 15-May-17 14:09
553 Relaying disallowed as <private outlook account>