Is an MX record required for domain alias?

[Julian2]

Hi, I've added my domain alias in Google Workspace, but I'm unsure of what to do next. I don't want to setup Gmail for the alias, I just want all emails sent to users at that to go to the same user at the primary domain. The domain alias is a subdomain. 

Primary domain: example.com

Domain alias: one.example.com

I presume I need to add an MX record so that email to user1@one.example.com goes to user1@example.com - is that right?

Thx

[cryptochrome]

If one really is a subdomain of the other, e.g. both have the same top level domain as in your example.com, an MX record at the root of the domain is enough. You would only need an additional MX record at the sub-domain level if you wanted to route mails for that sub-domain differently. 

That said, if these are entirely different domains, like example-1.com and example-2.com, each domain will need MX records pointing to Google. 

[Julian2]

Thanks, one is a subdomain of the other: example.com and one.example.com

I haven't added any additional MX records yet and I can send from the subdomain by switching sending with Gmail. But I can't receive email at the subdomain. Messages sent to those addresses fail. So I presume I need to do something, I'm just not sure what. Any ideas?

[cryptochrome]

From a DNS standard perspective, adding the MX records at the top level of your domain automatically includes all sub-domains, unless overridden with individual MX records per sub-domain.

Now, it might be entirely possible that Google still wants you to "activate" the domain before they accept incoming mail. I would try two things:

1.) Try to activate Gmail for the subdomain and see what happens. If Google adheres to the standard, it will see the top-level MX and be fine with it and activate Gmail for it. If not, try:

2.) Copy the MX record from your top level to the sub-domain, then activate Gmail. This should work 100%. 

[Suvegas]

Can you please help to provide the source of this info or the RFC link that mentions your info.

I'm trying to find RFC that mentions MX defined for the main/top-level domain is sufficient and this MX would be available for sub domains under it .

[KAM]

@Suvegas See https://datatracker.ietf.org/doc/html/rfc5321 Section 5.

Regards,

KAM

[Anuj_Anish_HP2]

I have a similar / additonal query - in my case i want the primary domian(abc@example.com) to be redirected to a cloud Email Gateway (MX redirection) and be scanned for both inbound outboud email, but the secondary domain(abc@xyz.example.com), i just want that it gets routed via Gmail itself without the need to forward to Cloud mail Gateway. What would be needed in this case to be done on Gmail Routing?

[bourroush]

Hi @Julian2 . Did you manage to make it work in the end ?

Thank you