Hello,
How do we write attn when addressing someone?
Attn: Smith,
Thank you for your letter (etc. etc.).
Do we need a comma or any punctuation mark after the person's name. Is colon after attn okay?
Thanks,
Mr. X
A colon after Attn is sufficient, but you need to use Mr before Smith.
As far as a comma after Smith is concerned, recently this appears to have become a matter of personal choice. Some people will write:
Dear Mr Smith,
---
Yours faithfully,
Mr X
(commas after Smith and faithfully).
Others will write:
Dear Mr Smith
......
Yours faithfully
Mr X
(no comma after Smith or faithfully).
Business letter styles may differ by country, but in the U.S. the "attention" line is usually typed in all capital letters thusly (with a colon after the "ATTN"):
ATTN: MR. WALTER FEEGUS
You should not address a letter as ATTN: SMITH unless your recipient is generally known by only one name (like Cher or Bono). It is acceptable to address it ATTN: MR. SMITH or ATTN: JOHN SMITH, but not by surname alone.