The right sign for "mail" depends on what you mean.
If you are talking about email then see: EMAIL
If you mean "mail" as in the noun "a piece of mail or a letter," then use
the version of the sign that looks sort of like licking a stamp and putting
it on the corner of an envelope:
MAIL as in a piece of mail, a LETTER:
If you mean "mail" as in the verb form "I need to mail a letter," what you
are really saying is that you need to "send" a letter. In that case use the
version of the sign for "send" that looks as if you are throwing a wad of
There are several versions of the sign for "postage" or "stamp." I use
the "H" handshape moving from near the lips to the corner of my hand
version. The "H" handshape is about the width of a stamp. The
flat hand is similar to the size of an envelope. Thus this version of
the sign for "postage" is very visually similar to the concept it is
representing. However, you should always do the version used by your
local teacher or Deaf Community.