First, see thread here on similar issue. You may want to post there too to broaden awareness.
The first thing to do is make sure your vacation IP isn't on any blacklists. You can find your IP by googling "what is my IP address" or go to IPChicken.com. To check that IP against blacklists go here. If on a blacklist there are procedures to get off. Some delistings are easier then others.
After that you also have to make sure that IP address has a PTR record. That is more a luck of a draw kind of thing since there isn't much you can do if your ISP doesn't list their IPs. You could set up a VPN between your home router and vacation router and router the traffic that way but that depends on hardware.
