Hi,

I receive the following message when trying to send an email to any sender (internal or external):

Unable to send message;Reason:554 5.1.8 Sender Address Blocked

Other users on our domain are not experiencing this issue.

Could you please fix this or let us know how to fix it?

Thank you!

Edit: I think this might have happened because I wrote requests for offer with the same text to six different vendors. If this is a kind of spam detection it is too sensitive to trigger after a low number of mails, all of which were answered by the recipients.