They dropped that requirement a long time ago. I just use #123, let the imaginations run wild.

Given even the USPS' own Click N Ship web site doesn't even build addresses according to the req's, how do you expect them to enforce them?

See the post above this one (from RogerD408), but also:

In my case, it's in the form of "Suite 123-456", where "Suite 123" is the actual official number of that UPS Store within a strip mall (the street address covers the whole strip mall), and the "456" is the only part that is my actual personal mailbox number.

One or two places that I did my address change did require me to say "Suite 123 PMB 456" because their system couldn't take "123-456" or even 123456" as a Suite number, but the rest of them are happy with "123-456", or in some cases "123456" because they can't take the hyphen (or can't take a Suite number longer than 6 digits total).

http://pe.usps.gov/text/pub28/28c2_040.htm says that the current regulation is to use either "PMB" or "#".

It isn't enforced, but it's there.

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