ovirt in version 4.2 choose to incorporate postfix as a mandatory MTA: yum erase postfix ... Removing: postfix x86_64 2:2.10.1-6.el7 @base 12 M Removing for dependencies: cockpit-ovirt-dashboard noarch 0.11.28-1.el7 @ovirt-4.2 15 M ovirt-host x86_64 4.2.3-1.el7 @ovirt-4.2 11 k ovirt-hosted-engine-setup noarch 2.2.22.1-1.el7 @ovirt-4.2 2.2 M Is there a way to change that ? It's not about postfix being inferior or superior to other solutions. It's that it didn't ask any thing, didn't check if one was already installed. It's just installed. For example: rpm -q --provides postfix MTA config(postfix) = 2:2.10.1-6.el7 postfix = 2:2.10.1-6.el7 postfix(x86-64) = 2:2.10.1-6.el7 server(smtp) smtpd smtpdaemon rpm -q --provides sendmail MTA config(sendmail) = 8.14.7-5.el7 sendmail = 8.14.7-5.el7 sendmail(x86-64) = 8.14.7-5.el7 server(smtp) smtpdaemon There is a lot of other dependencies to declare other than postfix, MTA would have been better.