Why do I need to use someone else's SMTP server?

Factual Questions
1

I use my ISP’s SMTP server for outgoing email (Verizon FiOS). What is so special about an SMTP server that I can’t just have a private one locally on my own computer? I have a CS background, have been known to send emails by telnet to SMTP servers, etc., but this never occurred to me before. My ISP does things like freeze my account if an email has too many addresses in the To field (I guess they don’t want me to be a spammer), or if I try to send traffic to somebody else’s SMTP server (haven’t quite figured out why they don’t like that). But an SMTP server can’t be very complicated to implement. So why aren’t they just bundled with email clients?

2

Theoretically, nothing. Practically, lots of ISPs know IP addresses ranges used by household connections and block incoming emails from those addresses, because malware writers thought of this long ago and set up malware that included small smtp servers so that infected PCs were sending out spam.

3

Also, many ISPs block outbound SMTP traffic from home broadband connections, for the same reason dzeiger gave. Often running a mail server is only permitted on a business account.

4

This is exactly why I have business class internet service at home instead of consumer class. I get a static-IP address that is not in a “dialup” block and my contract specifically allows me to run my own servers, including mail and web. Business class only costs me $0-10/month more than residential internet, depending on discounts, etc.

5

Back in the early 90’s I knew several people running their own mail servers. Linux had several to pick from. Pine?? I think was one. I can’t recall if Pine was a server or client. But, I know Linux had several that were popular.

But that got blocked long ago. Stinking spammers ruined it for all of us.

6

I run a home SMTP/POP server. Very handy, lots of easy to generate addresses to cut down spam to my real addresses. Incoming and outgoing, but only really use incoming. Just a regular ISP.

Also a computer guy, so “I know what I’m doing”.* So I love having all ports open, but don’t want that for the usual idjits. Kinda conflicted there.

  • I get surprisingly few “probes” per day. Rarely more than 3, sometimes none. Reading logs is a lot of fun sometimes. Seriously.
7

As noted, there’s no reason you can’t. I ran a mail server for a little while on my home machine to try something out, but I really have no particular reason to do so. Once I quit experimenting with it, I uninstalled it, and never used it for my real mail. If you register your own domain, most of the registrar services let you generate multiple addresses, which is what I do.