Linux distributions like RedHat and Fedora ship with two Mail Transport Agents (MTAs) - sendmail and postfix . But at a time, you can use only one of the two - ie either sendmail or postfix. You can switch between the two very easily by using the 'alternatives' command.
With alternatives, an executable with a generic name on the filesystem is used to access a particular service. This executable is really a symbolic link to another symlink in the /etc/alternatives/ directory. For example, the '/usr/bin/sendmail' is actually a symbolic link to /etc/alternatives/mta . In order to select between sendmail or postfix, we just change the symlink for the /etc/alternatives/mta . This is normally done with the alternatives command. Here are some examples:
To display which MTA alternative is in use:
With alternatives, an executable with a generic name on the filesystem is used to access a particular service. This executable is really a symbolic link to another symlink in the /etc/alternatives/ directory. For example, the '/usr/bin/sendmail' is actually a symbolic link to /etc/alternatives/mta . In order to select between sendmail or postfix, we just change the symlink for the /etc/alternatives/mta . This is normally done with the alternatives command. Here are some examples:
To display which MTA alternative is in use:
# alternatives --display mta# alternatives --config mta# alternatives --set mtaRedHat/Fedora has got a GUI for switching between the MTA's which is redhat-switch-mail.
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