I'm new to Linux but have messed around a little with installation of
different distributions.

However, I have no clue on how to effectively setup DNS or an MTA like
Sendmail. 

Can anyone point me to some good resources that I can use for reference
purposes?

Also, what MTA is the most popular?

I would really like to be able to setup whichever MTA it is to filter
content as it comes in and strip unwanted attachments.

Thanks,

Chris