Procmail regexp question

  For one of my filters I need to find one of "smtp" or "esmtp".
I have a gut feeling that there is something more elegant than
"(s|es)mtp".  Any help on this?

-- 
Walter Dnes <waltdnes(_at_)interlog(_dot_)com> procmail spamfilter
http://www.interlog.com/~waltdnes/spamdunk/spamdunk.htm
Why a fiscal conservative opposes Toronto 2008 OWE-lympics
http://www.interlog.com/~waltdnes/owe-lympics/owe-lympics.htm