Man pages matching name sendmail in section 1:

sendmail.1.en	debian 10 / citadel-server
sendmail.1.en	debian 10 / courier-mta
sendmail.1.en	debian 10 / nullmailer
sendmail.1.en	debian 10 / postfix
sendmail.1.en	debian 11 / courier-mta
sendmail.1.en	debian 11 / nullmailer
sendmail.1.en	debian 11 / postfix
sendmail.1.en	debian 12 / courier-mta
sendmail.1.en	debian 12 / nullmailer
sendmail.1.en	debian 12 / postfix