Envelope rewrite by sendmail?

[Trond Endrestøl]

Hi,

I have users with email addresses ending in a long suffix.  Combine 
this with long names in front of the @ sign, and it immediately gets 
very tedious to type an email address.

We have a shorter domain name, and I was thinking of creating a small 
SMTP server to serve this short domain name and simply forward email 
to the main SMTP server.

It is not possible to switch the main SMTP server to serve the short 
domain name.

Here's an example:

  A mail messages arrives on the small SMTP server addressed to
  shorty at short.tld. Sendmail, though the aliases mechanism, forwards
  the message to long.name at some.incredible.long.domain.name.tld.

  Antispam measures such as SPF will flag the small SMTP server as not
  allowed to send email on behalf of the originator.

  Thus, prior to forwarding each message, the small SMTP server will
  need to masquerade as the originator and rewrite the envelope's from
  address to an address within the short.tld domain.

Can this be accomplished using sendmail? Would the short address of 
the receiver suffice or should I use a fixed address regardless of the 
originator and/or the ultimate receiver?

The OS on the small SMTP server will be FreeBSD 11.

Any pointers are appreciated.

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