Email to pager gateways often use all-numeric addresses. I'd suggest
caution in deploying something like this. As an "FYI", Pagenet uses
something like 1231234567(_dot_)1234567(_at_)pagenet(_dot_)net for an address.
Yes, you
probably won't see this often, but it can happen.
On Tue, 24 Feb 1998 gsutter(_at_)pobox(_dot_)com wrote:
It allows for a single letter, if present, then a string of numbers
until an @ sign, OR for anything up to @, then a domain name consisting
of a string of numbers followed by .com.
Since there are some domains made up of just numbers (e.g. 2600.com), an
exceptions list must be made. Annoying, yes, but probably worth it.