How do I allow only my domain and some external domain to post to Google Group via email

Question

Currently I got this to work so far:

I got Google Apps for Work for my company "Contoso" and I have set up a distribution list via Google Groups so that anyone in the company can send an email to [email protected] and only members of the support group will receive it. All external users will get a bounce if they try to send an email to this list.

I am stuck on the next bit, we got close partnership with people with @partner1.tld and @partner2.tld, and wish to open up our techsupport list to them too, but not anyone else on the internet... how do I do that?

Currently there is only one email address for @partner1.tld, and not many for @partner2.tld, so if we were to add extra addresses that are allowed to post the the list that might work for a while too.

EDIT: basically we just need techsupport list to reject all emails unless they are from @contoso.tld, @partner1.tld and @partner2.tld.

Answer 1

There is no way to do this currently, but there is one thing you can do

1. Create a group with the same members and add the additional external emails to the group as well
2. Ask them to post on the group when required
3. Set permissions as restricted

Downside is that other people from their team will also get the email.