The Indianapolis Star: USPS is vital public service, not failed business venture | Letters
Unfortunately, I have not been able to find a USPS Web site which states this clearly, and so for the moment will refer to this Web page by another source (which has links to USPS Web pages which are no longer active ).
You're close: Attn. In a business letter, though, you're usually better off avoiding abbreviations, and some style guides recommend leaving 'attention' out entirely.
I strongly disagree with Deputy Opinion Editor Jacob Stewart's column, “Trump should dismantle USPS – we’d all be better off." Article I, Section 8, Clause 7 of the U.S. Constitution granted Congress ...