Office365 SMTP Email - 3rd party app error

[Dames]

Hi - this is possibly a bit of a long shot, but I've been experiencing an error recently when attempting to trigger an SMTP email send (through a 3rd party application) via the smtp.office365.com server:



I've tried researching a bit, but most of the results I have found on Google seem to indicate this usually has something to do with remote desktops. I am not using a remote desktop, nor does the third party application have an option as such, but I'm at a bit of a loss as to what else it could be. Checked AV, Firewall, etc.

I don't suppose anyone has any ideas? This is on Windows 11.

Thanks!

 

[aybbleek]

What is the 3rd party application? Also check SFP, DKIM, DMARC for the domain in question is in line with this. Also note that if the application/service doesn't support TLS 1.2 it will not work with O365 SMTP

 

[InvisibleJim]

I can't think of a reason why it would throw this error but it might be worth checking if the account you are using to relay has multifactor authentication enabled or blocks legacy authentication (SMTP, IMAP, POP etc) both of which are M365 security best practices.

 

[ubercal]

Hi - this is possibly a bit of a long shot, but I've been experiencing an error recently when attempting to trigger an SMTP email send (through a 3rd party application) via the smtp.office365.com server:

View attachment 1207994

I've tried researching a bit, but most of the results I have found on Google seem to indicate this usually has something to do with remote desktops. I am not using a remote desktop, nor does the third party application have an option as such, but I'm at a bit of a loss as to what else it could be. Checked AV, Firewall, etc.

I don't suppose anyone has any ideas? This is on Windows 11.

Thanks!

read up on the microsoft help site.They explain the 3 methods to use o365 as an smtp relay.Its abit of a hit and miss.Personally i would just sign up with a 3rd party smtp relay service cause it "will just work".