if you create a new outgoing message in entourage and set the account, one would think that the signature used would be the default signature for that account. but it is not. there appears to be no other way to set the signature for the outgoing message. (signature is not a property of a message!) it is possible to get the content of a signature you want to use for an account. however, it does not help because the signature of the default account has already been appended to the message.
this is a complicated work around, but it seems it is a MS Entourage bug, and a long standing one at that.
here’s a related thread:
http://bbs.applescript.net/viewtopic.php?id=5787
-- unique matching string of the email account of the desired pop account to send from:
property acctemail : "woodenbrain" -- obviously unique to my case here -- put in your own
-- test variables:
property thename : "BILLYBOB"
property theemail : "billybob@test.com"
property subjecttext : "Test subject"
property replytext : "some reply text" & return
tell application "Microsoft Entourage"
set replytext to "Dear " & thename & "," & return & return & replytext
-- get the desired account as an object
set theaccts to every POP account
set desiredacct to ""
repeat with i from 1 to (count theaccts)
set anacct to item i of theaccts
if email address of anacct contains acctemail then
set desiredacct to anacct
exit repeat
end if
end repeat
-- get the actual signature of that account
if desiredacct is not "" then
set sig to ""
set dst to default signature type of desiredacct
if dst is "other" then
set dsc to default signature choice of desiredacct
set sig to content of dsc
end if
-- set the reply text to the original reply text and the signature
if sig is not "" then
set replytext to replytext & return & return & sig
-- the only odd thing is that "return & return" seem never to be added
end if
end if
set thereply to make new outgoing message with properties {recipient:theemail, subject:subjecttext, account:desiredacct}
-- content must be set on separte line, because if you set content as a property of the outgoing message, Entourage will erroneously include the default POP signature
set content of thereply to replytext
end tell