Description of problem: Application of update to sendmail replaced a customized /etc/sendmail.cf with the default sendmail.cf, and saved the old version as /etc/sendmail.cf.bak. This broke my mail server, it seems like the new sendmail.cf should have been saved as sendmail.cf.rpmnew Version-Release number of selected component (if applicable): 8.14.1-4.2 How reproducible: change /etc/mail/sendmail.cf to (say) allow external connections, and then run "yum update sendmail" -- tada! A default sendmail.cf overrides the changes.
I am sorry, but changes should be made in the sendmail.mc file in /etc/mail. /etc/sendmail.cf gets automatically overwritten if there is a change in any of the mc files in /etc/mail.