Google Workspace: emails sent from secondary domain show the “mailed-by” field from the primary domain

emailg-suitegmail

TL;DR: two domains in Google Workspace. The email sent from the second domain show the first domain as "mailed-by"

Google Workspace configuration

In my Google Workspace account I've two domains:

  • primary-domain.com: my primary domain
  • secondary-domain.com: a secondary domain added as a "domain alias"

I configured both the SPF and the DKIM for both domains.

The DKIMs were generated by Google Workspace and they show as OK in Google Workspace.

Gmail configuration

From my Gmail account (the one of primary-domain.com) I added the secondary domain via "Send mail as". Since Gmail recognizes it as the secondary domain for the same account, it doesn't require to insert neither the SMTP credentials, nor the verification code.

Initially I checked the Treat as an alias checkbox.

The sending account is readily available and I can send email either with my primary or my secondary account.

The problem

The only problem I've is that when I send an email via my secondary domain, the recipient sees the first domain as mailed-by (note that the signed-by is OK)

What I tried

The only other thing I could think of was the Treat as an alias checkbox in my Gmail, so I unchecked it. Still, it doesn't make any difference.

Yes, I know that re-adding the secondary domain as "not a domain alias" would probably fix the issue, but that is a totally different scenario and I don't want to do that.

Any other ideas?

Best Answer

After a chat with an Email Specialist from Google, this is what I got:

Please note that this is an expected behaviour.

In the sender side, it will show the alias domain but in the recipient end it will show the primary domain for the authentication purpose.

Since all the authentication happens in the recipient end.

As you are using primary email address with credentials to send emails using your alias email address so in the recipient end you will get both the primary domain and alias domain for the email authentication.

So that's it. I could probably try and fiddle with an external SMTP to make it work, but I'm not going to invest any more time on this.

Related Topic