[quoted text] For an email server to send and receive email with other servers on the internet, they need port 25 to be open. Unfortunately, ISPs in the U.S. block port 25 by default, a practice started in the 90s when home computers were hacked and turned into open relays abused for spamming. Sometimes it’s possible to get this port unblocked, but it’s not uncommon for the ISP to ask for a significantly more expensive class of service in exchange.
ISPs also typically assign dynamic IPs to residential internet connections. Large email service providers block residential dynamic IPs en masse also due to the issue raised above. While it’s possible to get a static IP address from your ISP, they will charge for it and potentially require a more expensive class of service. PTR records, or reverse DNS, is also a key requirement for trustworthiness when setting up an email server. Getting this type of record with a residential internet connection can be a significant challenge and may also incur additional costs.
To summarize, port
blocking, dynamic IPs and challenges in establishing a PTR record all
interfere with easily running an email server at home. It can cost
hundreds of dollars per year and consist of a significant investment of
time with your ISP to get things set up just right. After thinking about
this problem and experimenting for a while, we managed to find a better
way.
[end quoted text]
Thanks,
Mike