Most ISP's nowadays block port 25, as it's used for mass mailing. If you're on one of those ISP's you can use port 26 instead. Port 26 is enabled by default on our shared hosting servers and is ready for your use.

* Please note, that if port 25 is working for you, it might be a temporary thing as ISP's notice mail traffic passing and automatically close ports. It might not be instant, but to be safe, we still suggest using port 26.