On 6/15/21 12:13 PM, Mike Peckar via WLUG wrote:
[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 [...] 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. [...]
Port 25 access is not blocked by Charter in central MA, anyway. Perhaps it is blocked elsewhere. My IP address has changed about 4 times in the past 7 years or so. When it changes a script of mine warns me, and I go edit my DNS to change the MX and SPF information there. This all takes perhaps 5 minutes. If you don't want to watc hyour home IP as carefully, you could run a backup MX server in some more IP-stable location, i.e., a VM off in Amazon EC2. Certain domains will flat-out refuse to accept email which originates from a RESIDENTIAL network block. The only one I've encountered though is Comcast. Email sent to addresses @comcast.net are refused, even when the email passes all the tests (SPF, DKIM, DMARC etc). Mail sent to GMAIL, YAHOO, various microsoft/azure addresses etc, all work. I presume that if you want your mail to be accepted from everywhere, you should get a business plan from your ISP. Depending on what you'd like to add on top of your mail service things can get more complicated, but email itself isn't too bad. Test out your setup before exposing it to the internet, and make sure it doesn't accept email for domains other than your own. If you run an open relay email server that's a very good way to get shut off. --MCV.