Description of problem:
Imagine you've a SMTP relayhost/smarthost with a SSL certificate having the 
common name "mail.servername.tld". If I configure the following in .muttrc:

  set smtp_url="smtp://tux.tld"

and try to send an e-mail via mutt, mutt of course complains that the name
of the hostname doesn't match with the certifiate and offers the following
possibilities.

  (r)eject, accept (o)nce, (a)ccept always

If I choose "(a)ccept always", a copy of the certificate gets saved into the
.mutt/certificate file - as expected. Then I'm quitting mutt and starting it
again. I'm trying to send another e-mail. Unfortunately, I'm getting the same
possibilities as before listed again:

  (r)eject, accept (o)nce, (a)ccept always

If I choose "(a)ccept always" again, the certificate gets saved another (!)
time in .mutt/certificate. That means the certificate is saved there twice.
And if you do this a third time, it's there a third time. Which seems wrong
to me.

I'm expecting, that if I added already the first time an exception by using
the "(a)ccept always", it never should ask me again and just sent the e-mail
silent without bothering the user. That's at least how e.g. Firefox is doing
this right now for exceptions.

Version-Release number of selected component (if applicable):
mutt-1.5.20-2.20091214hg736b6a.i686

How reproducible:
Everytime, see above.

Actual results:
Mutt doesn't honor "(a)ccept always" as expected if certificate name doesn't 
match.

Expected results:
Mutt should honor "(a)ccept always" as expected - even if certificate name 
doesn't match.