A user is unable to send email and the error below is received:
smtp.eu1.exclaimer.net gave this error: Access denied, bad outbound sender AS(41000001)
This error occurs because Office 365 has banned the user from sending email, because they are deemed to have sent excessive levels of outbound spam.
A user can be de-listed as per the guidance in this article.
Note: before requesting for a user to be de-listed, you should ensure that their account/computer has not been compromised, and that its not being used to send unsolicited email - otherwise the user could be banned again.
Handling a compromised account
To resolve a compromised user account:
- If you are an administrator, see guidance in this article
- If you are a user, see guidance in this article
You can configure Office 365 to send notifications when outbound spam mail email is detected, or if a user has been banned by Office 365. To do this, update Outbound Spam Preference settings in the Exchange Online Admin Console, as per this article.