mh-e: Signature
9.4 Inserting Your Signature
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You can insert your signature at the current cursor location with the
command ‘C-c C-s’ (‘mh-insert-signature’).
By default, the text of your signature is taken from the file
‘~/.signature’. You can read from other sources by changing the option
‘mh-signature-file-name’. This file may contain a “vCard” in which case
an attachment is added with the vCard.
The option ‘mh-signature-file-name’ may also be a symbol, in which
case that function is called. You may not want a signature separator to
be added for you; instead you may want to insert one yourself. Options
that you may find useful to do this include ‘mh-signature-separator’
(when inserting a signature separator) and
‘mh-signature-separator-regexp’ (for finding said separator). The
function ‘mh-signature-separator-p’, which reports ‘t’ if the buffer
contains a separator, may be useful as well.
A signature separator (‘"-- "’) will be added if the signature block
does not contain one and ‘mh-signature-separator-flag’ is on. It is not
recommended that you change this option since various mail user agents,
including MH-E, use the separator to present the signature differently,
and to suppress the signature when replying or yanking a letter into a
draft.
The hook ‘mh-insert-signature-hook’ is run after the signature is
inserted. Hook functions may access the actual name of the file or the
function used to insert the signature with ‘mh-signature-file-name’.
The signature can also be inserted using Identities. 
Identities.
Info Catalog
mh-e: Inserting Messages
mh-e: Editing Drafts
mh-e: Picture