Mutt/Sendmail Masquerading Problem on AIX 5.3

We are running Unix AIX 5.3 and I have been asked to masquerade the sender name on our email processing.
We have one domain name and many users:
user1@domainname
user2@domainname
user3@domainname

We use mutt/sendmail to do our email processing.

I discovered that using genericstable within sendmail covered this.
So I created a genericstable:
user1 new1@emailaddress
user2 new2@emailaddress
user3 new3@emailaddress

and amended sendmail.cf to take in:
Kgenerics and Ruleset 93

and then started doing some testing.

This works well when using mail:
mail -s "test" deliver@address < /dev/null
If run from user1 the sender address becomes new1@emailaddress

However if run from mutt the result is not what I want:
mutt -s "test" deliver@address < /dev/null
If run from user1 the sender address remains user1@domainname and doesn't become new1@emailaddress.

I can't see where the problem lies as surely mail and mutt must be using sendmail and yet mutt must be ignoring the genericstable.

Has anyone experienced anything similar?

Many thanks.
Francisco Martins

i used to administer Postfix not sendmail but anyway recheck parameter masquarade domain or something like that.. or check what mail.log and other log file writes... maybe u get some useful info from there