Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
If you control satellite systems which need to relay their mail through a centralized host for sending then you have several choices. Perhaps the simplest software to use is the nullmailer program.
In the past we've looked at setting up exim, postfix, and sendmail forwarding but if you're not expecting to send much mail, and you don't need much processing then running a full mailserver is probably overkill.
The nullmailer package is very simple to configure and install.