Sending Mail Newly Created Internet Domains

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How do I send mail to newly created Internet domains?

The MTA is normally configured to validate the top level domain (TLD) in remote addresses. The internet.rules file in the config directory contains a list of all the valid TLDs. However, the Internet Corporation for Assigned Names and Numbers (ICANN) does create new TLDs from time to time. The most recent additions have been .cat (Catalan), .mobi (mobile devices and associated content), and .travel. Users attempting to send mail to invalid domains will receive the error:

SMTP Error: 5.1.2 unknown host or domain: address@domain"

Patch releases from Sun normally include an up-to-date internet.rules file. If you don't have an updated patch release, or don't want to install a patch for other reasons, a quick fix is to add additional lines for missing domains to the bottom of the internet.rules file in the config directory. Simply copy an existing entry like

!    Catalan
.CAT                 $U%$H$D@TCP-DAEMON

and modify the right hand side as appropriate. You then need to run imsimta cnbuild and imsimta restart.

Another alternative is to disable the TLD validity checking entirely. This is done by removing the include of internet.rules from imta.cnf and replacing it with a wildcard dot rule of the general form:

.                    $U%$H@TCP-DAEMON

This eliminates the need to periodically update the domain list at the expense of no immediate checking for invalid addresses.