Hello everyone,

I need some help trying to integrate my company emails into Zoho CRM system, for which their O365 Email Integration keeps failing.

My company User Principal Name, used in Active Directory (user@mother-company.com) is different than primary email (user@child-company.com)

This is because there are multiple subcompanies inside our group, and we all have the same domain in our User Principal Name’s, but we use our company email for communications.

At first, I thought it was something related to my tenant demanding for OAuth authentication, but even using the O365 connection that provides it, it keeps failing with the following error:

Unable to Get SMTP Email - Outgoing Authentication Failure for : user@child-company.com : 535 5.7.3 Authentication unsuccessful

SMTP Auth is enabled for my user following this instructions: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission

The thing is, we tried with a test account, which it’s primary email matches the user principal name (both user@mother-company.com) and thing worked smoothly with the Office 365 email integration.

Any ideas?