Excel: Grabbing primary SMTP address from an Exchange 5.5 export

This is an Excel function that allowed me to grab the primary SMTP address from an Exchange 5.5 export of users: -

=IF(ISERROR(MID(R18,FIND("SMTP",R18)+5,FIND("%",R18,FIND("SMTP",R18)+5)-FIND("SMTP",R18)-5)), RIGHT(R18,LEN(R18)-FIND("SMTP",R18)-5), MID(R18,FIND("SMTP",R18)+5,FIND("%",R18,FIND("SMTP",R18)+5)-FIND("SMTP",R18)-5))