Alias domains

What an alias domain does, what it cannot do, and how to swap one with your primary domain.

An alias domain inherits the mail configuration of its primary domain. Mail addressed to someone at the alias is delivered to the same person on the primary domain, so bob@example.com reaches the mailbox that bob@example.co.uk reaches. Once it is set up there is nothing further to configure.

What an alias domain cannot do

An alias has no settings of its own. You cannot give it different spam filtering, or send its mail somewhere else, because it takes everything from the primary domain.

You also cannot make one address behave differently on each domain. If sales@ on the primary reaches a shared mailbox, sales@ on the alias reaches the same one.

Mail arrives at the primary domain address rather than the one the sender used. Where your own server routes mail by the domain in the address, that difference matters, so check the routing before adding an alias.

Delivering an alias to more than one person

An alias cannot deliver to several mailboxes. Use a distribution list instead, which is built for exactly that. See how to create a Zimbra distribution list.

After you create one

An alias domain created in the control panel takes about 30 minutes to reach all our external servers. Mail addressed to it before then may not be delivered, so wait the half hour before testing.

Swapping the alias and the primary domain

Sometimes a domain that started as the alias becomes the one you want to send from. There are two ways to change that, and the simpler one is often enough.

The first is to leave the domains as they are and change the From address on each mailbox, using the Persona feature in Zimbra webmail preferences. Nobody's login changes, and mail to either domain still arrives.

The second is to move every mailbox onto the other domain, which makes it the primary in every sense. It is more work, and mail may bounce while you are part way through, so do it at a quiet time.

The steps below assume both domains already have MX records pointing at Zimbra. They use domainA.com as the current primary and domainB.com as the current alias.

1. Delete domainB.com, the alias domain.
2. Provision domainB.com as a Zimbra domain in its own right.
3. In the control panel, edit each mailbox and change its domain from domainA.com to domainB.com. Changing the domain is what moves the mailbox.
4. Do the same for distribution lists and resources.
5. Check that domainA.com is empty, with every mailbox, alias, distribution list and resource now on domainB.com.
6. Delete domainA.com.
7. Provision domainA.com again, this time as an alias of domainB.com.

Afterwards everyone signs in with their domainB.com address, so every device needs its username updated. In our experience IMAP, mobile and Outlook Connector clients do not need a full resynchronisation of the mailbox after the change.