[MlMt] Attachments

[Randall Gellens]

Encoding binary attachments as text expands to about 3x the size, but 
many modern mail servers support the ability to transmit binary data, so 
encoding as plain text is not needed when if your mail submission server 
and MailMate both support this extension. I haven't tested if MM 
supports it.

Note that even if both MM and your mail submission server both support 
the extension, the next-hop server (e.g., the recipient's receiving mail 
server) might not, forcing the mail server that has the message to 
encode it for transmission.

Also note that any server may reject an incoming message as being too 
large.

--Randall