The best replacement for sendmail is postfix.

The best alternatives to sendmail are rated as following:
★★★★★  postfix
★★★  exim
★★★  smtp
★★★  qmail
★★  mailx
★★  mail
★★  exchange
★★  postfix ubuntu
★  postfix centos
★  php mail
  ssmtp
  phpmailer
  mutt
  dovecot
  exim4
  ms exchange
  exchange server
  procmail
  postfix better
  postfix redhat
  microsoft exchange

Your alternative for sendmail is not listed? Suggest!
Speaking about sendmail, one probably shouldn't forget about attachment.

Other search terms related to sendmail and their ratings are:
★★★★★ attachment
★★★ subject
★★ postfix
★ perl
★ attachments
★ dovecot
★ tls
auth
sendmail
courier imap
You have in mind a companion for sendmail and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of sendmail in all years. Click on graph for more.
sendmail
postfix
exim