php/mysql blues...

I'm having some trouble getting a query right.  I'm hoping that someone here can help me.
I'm doing this on a 3.23 server btw.
I have a table that has three columns, mail_from, mail_to, ip_address.

I'd like a list of instances where there are multiple duplicate mail_from and mail_to entries, but different ip_addresses.
The trouble that I'm running into is limiting it by a count of multiple columns.  It can't just be multiple instances of one column, it has to be the combination of the two. 

so if the table looked like
mail_from - mail_to - ip_address

a@a.com - b@b.com - 3
a@a.com - b@b.com - 4
c@a.com - b@b.com - 2
b@a.com - a@a.com - 2
d@d.com - a@a.com - 3

I would get back
a@a.com - b@b.com - 3
a@a.com - b@b.com - 4


If anybody could give me a hand with this, I'd appreciate it alot.  If you need any clarification on what I'm asking for feel free to post questions.

Thanks!