I have multiple users of our exchange email system that work from their home office and the on the road. These users are currently7 setup to use POP/SMTP protocols for sending and receiving. We have have a big issue in regards to ISP's blocking port 25 for SMTP sending. Because the high volume of traveling these users are constantly going through different ISP's (airports, hotels, home, cafe's etc.). We've come up with two main ideas for solutions, and I was looking to see if anyone had any Pro's and Con's or suggestions.
Our 2 ideas are:
Setup RCP over HTTP for external Exchange protocol use - Issue here is we do not currently have a front end server set up, but do have multiple exchange servers
Open an new Port for SMTP send - We do see any extra ports open to be a security risk. Also consider opening ports for SSL or TLS.
Any suggestion would be greatly appreciated