So here’s a handy guide to the single-letter abbreviations you can safely use for your English-language contact details.
T Telephone — the person’s phone number.
M Mobile — the person’s mobile phone number.
F Fax — the person’s fax number.
E Email — the person’s email address.
W Web — typically the general company website.
See full article at http://thunderguy.com/semicolon/2008/08/08/p-is-not-for-telephone/