For Google Apps users: Cross-Domain Email Address References

Image credit: Beau Giles

Recently I reconfigured my primary email address setup to get over some specific issues I was having with inbound email from one particular client. I run one domain in Google Apps, which includes this address. The work consisted of deleting the current address, which was actually a group set up on the domain (which redirected to multiple email addresses) and creating a new Google Apps user with the same email address to replace it. After the change, I retrieved all my email from that Google Apps user.

To summarise with an example:

BEFORE: foo.bar@baz.com was a Google Apps group on domain baz.com, containing the external email addresses my.other.email@isp.net and my.mobile.email@gmail.com allowing incoming email to be forwarded to those two other email addresses

AFTER: foo.bar@baz.com was a Google Apps user on domain baz.com

From an outside viewpoint, foo.bar@baz.com remained a valid email address, apart from perhaps a very brief period when I was doing the actual work. I expected that after the work, all email would continue to be delivered. This proved to be incorrect.

Following the changes, I noticed that I was no longer receiving emails from a couple of distribution groups, which fortunately I run, using another, entirely separate, domain which is also managed on Google Apps. In other words:

mygroup@somewhere-else.com contains a number of external addresses to distribute incoming mail to, including foo.bar@baz.com

Realising that I was no longer receiving email via this route, I logged in to the Google Apps control panel for somewhere-else.com and checked members of the group "mygroup", only to find that foo.bar@baz.com was no longer present.

So where had it gone? I am the only administrator for somewhere-else.com on Google Apps, and I hadn't removed it. It seems that Google Apps very cleverly checks email addresses to see if their domains are administered by Google Apps, and creates some kind of a link if they are. That way, if an email address is removed from a domain, that removal is propagated across Google Apps to other domains even if they are entirely separate.

I can see why this is a good thing to do, as it will reduce bounces. However, if you don't know about it, it can be difficult to track down if you're performing any operations which involve the temporary deletion of an email address, such as in this case.