Showing results for 
Search instead for 
Did you mean: 

Videotron email not working in Microsoft Office 365 Outlook for Mac


I just switched from Microsoft Office 2019 to Office 365 and set up my videotron email in my account as per what is required for incoming server, outgoing server as per the Videotron instructions online.  I can receive emails no problem but when I try to send anything I get an error message that says Technical details

SmtpSubmissionPermanent5XXException: Smtp submission failed. Server '' Port '465'. --> Unexpected SMTP server response. Expected: 250, actual: 550, whole response: 550 5.1.0 XqKsr70o5iOzJXqKvrpeaU AUP#EML-055
Failure code: 27a2

 How do I fix this?


Moderator - Solution Expert
Moderator - Solution Expert

Hi @JW787 From the SMTP error code 550 5.1.0, this indicates that the sending is completely interrupted instead of being retried. Then the code EML-055 indicates that the antispam filter is blocking the sending because the email used for sending is not a Videotron address. You would need to access your Outlook 365 settings and make sure the email address configured does not have any errors.  It would also be a good thing to check your SMTP server settings and to make sure the option "My outgoing (SMTP) server requires authentication" is enabled". The secondary option to use the same information as the incoming mail server to authenticate that is enabled by default can be left as it is.