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Why are you trying to run an MTA on a residential network? I suspect you are confused about how things work. The standard SMTP port (25) is for communication am

Why are you trying to run an MTA on a residential network? I suspect you are confused about how things work. The standard SMTP port (25) is for communication among MTAs and yes, residential networks block it (as they should) as any home PC sending on it is 99.999999999% likely to be part of a botnet. Sending mail from a home PC to the outside world is done by submitting it to an MTA on the SMTP Submission port (587) which your email provider should have given you credentials to. Home ISPs don't block port 587 AFAIK.

chrismorgan 3y ago
> 99.999999999% Eleven nines is very excessive. Frankly even six nines would still feel excessive, though I’m sorry to say that five might not be any more. Fifteen years ago, I think even three nines would have been excessive. Legitimate outgoing SMTP was fairly common in those days, and botnet SMTP probably proportionally rarer. You know what, even one nine might have been excessive less than twenty years ago.
kazinator 3y ago
You misunderstand the state of the e-mail world. Running an MTA on a residential network for receiving is completely fine. Sending mail directly from a residential network by connecting to the given mail domain is a nonstarter. Hasn't worked in twenty years or more. That doesn't require a MTA; only a MUA. Your mail program (MUA) like Thunderbird or Outlook, or the mail utility in a Unix-like OS, can perfectly well work without a configured SMTP server. You send to bob@example.com. The mail program will do a MX type DNS query for example.com and find out that the mail.example.com is the mail host for that domain. It will resolve that again with an A query to get an IP address, and connect to port 25 of that host to send the mail. In a world without spammers, that's how things would work. In a world with spammers, mail servers block connections from random addresses like residential IP addresses. Users (who want to send mail from home) have to resort to using forwarding hosts: their mail client is configured to make an SMTP connection not directly to a target mail domain, but to a configured host, like something run by their ISP or some commercial SMTP provider.

chrismorgan 3y ago

> 99.999999999% Eleven nines is very excessive. Frankly even six nines would still feel excessive, though I’m sorry to say that five might not be any more. Fifteen years ago, I think even three nines would have been excessive. Legitimate outgoing SMTP was fairly common in those days, and botnet SMTP probably proportionally rarer. You know what, even one nine might have been excessive less than twenty years ago.

kazinator 3y ago

You misunderstand the state of the e-mail world. Running an MTA on a residential network for receiving is completely fine. Sending mail directly from a residential network by connecting to the given mail domain is a nonstarter. Hasn't worked in twenty years or more. That doesn't require a MTA; only a MUA. Your mail program (MUA) like Thunderbird or Outlook, or the mail utility in a Unix-like OS, can perfectly well work without a configured SMTP server. You send to bob@example.com. The mail program will do a MX type DNS query for example.com and find out that the mail.example.com is the mail host for that domain. It will resolve that again with an A query to get an IP address, and connect to port 25 of that host to send the mail. In a world without spammers, that's how things would work. In a world with spammers, mail servers block connections from random addresses like residential IP addresses. Users (who want to send mail from home) have to resort to using forwarding hosts: their mail client is configured to make an SMTP connection not directly to a target mail domain, but to a configured host, like something run by their ISP or some commercial SMTP provider.