I told a rural mail carrier to stop putting junk mail in my mail box and from then on he stuffed it full each day for a while. Yeah he was a friend of ours
But seriously I have said this all my life, throw away your own junk mail Post Office. My freaking shredder is on overtime and such a waste of paper.
Do you have conduit from your house to your gate??? Private gate I presume? It's likely that the phone comes in from the street to the gate otherwise, you wouldn't have dialtone out there.
Heck, what a great opportunity to over-engineer something and get rid of your land line at the same time!? Maybe some directional wireless with a PTZ camera. Then use a web relay to open the gate (ControlByWeb.com sells them). Stick it all in a NEMA 4 enclosure... And you can do it all from your iPad, iPhone or desktop pc. And it'd pay for itself in about 3 years. Can I call you to sell you something like this!?
I always wanted to put in tastefully concealed cameras on the outside of my house... but wiring that stuff in right is a pain after the house is built. At least that's my excuse.