Having used 365 online with 4 accounts. I suddenly find I cannot send emails from any of them!
If I try and send from all the accounts....from a pc based email client or from the web mail I get the same error message come up
Your message couldn't be delivered because you weren't recognised as a valid sender. Make sure that your sending address is set up correctly and try to send the message again. If the problem continues, please contact your helpdesk.
This if from all addresses, to emails address that we have used hundreds of times. Because it happens on webmail as well it cannot be "our" problem.
This has been for a week now. Can anyone help please?
