I am trying to send an email using the smtp.office365.com server. It always return the same error:
5.7.57 Client not authenticated to send mail.
As far as I know, the problem is related with the fact that I'm working with ADFS. So I have previously federated my domain to work with Office 365. When I try to log in to Office, I'm redirected to the login page of my platform, which is fine.
Is there a way to send email using the Office smtp server when working with ADFS?
Not to my knowledge, you need to change the primary username to use your tenant domain rather than your federated domain. Then you'll be able to log in without ADFS.
We configured a single account for SMTP with just an Exchange Plan 1 license, and then set up internal SMTP relays using that account to transmit to O365. We then limit connections on that account to only known locations. Then we add SendAs permissions for that account to all the DLs/mailboxes that we need to send email from.
