I have an Exchange 2010 that has several accepted domains. Now I want this server to accept – besides the default SMTP domain – all subdomains of the default domain. The documentation in Technet states
When you create an accepted domain, you can use a wildcard character (*) in the address space to indicate that all subdomains of the SMTP address space are also accepted by the Exchange organization. For example, to configure Contoso.com and all its subdomains as accepted domains, enter *.Contoso.com as the SMTP address space.
It is, however not possible to add e. g. *.contoso.com if contoso.com is already configured. Exchange complains in this case that the domain is already configured.
It is also not possible to edit the "value", i. e. the domain name of an accepted domain. I know that I cannot modify the default accepted domain, but changing it to another does not help either, because the domain name itself can never be edited.
The last idea was deleting the accepted domain and re-creating it with "*." prepended. This is, however, also impossible because it is of course not possible to delete or modify the default address policy and if a domain name is used in an address template it cannot be removed from the accepted domains.
The question is: How can I make my Exchange 2010 server accept any subdomain of its default accepted domain with a wildcard?
Best Answer
you can use *.contoso.com as THE default and only SMTP address space. This should include contoso.com and subdomains.
This, however, does not help with sending emails from subdomain addresses, so you also have to provide users with smtp aliases, and you have to make sure the subdomains have proper SPF and MX records set if you don't want to end up in spam.
I have a small exchange setup with users who need to use country specific subdomains, so I have emails user@us.example.com and user1@uk.example.com. I have set those up as email aliases, and also set up accepted domains per country. That way I can keep track, and make sure I have all the DNS records set up properly as well. Plus a domain policy creates users in a per-country OU and groups, and with specific email aliases as defaults