setup POP3server for the internet

I have built several applications in delphi using the indy components suite(version 10.5.2 i think) and they all are working. I have just finished setting up the POP开发者_JAVA技巧3server and it works locally. I can see mail sent locally on there. I have been using "localhost" as my hostname. However, i want to graduate to a higher level of function. I want to be able to receive email from the internet such from msn, gmail, yahoo ... The problem is I don't know how to do this. What address should I be using inorder to do this? So far "myhouse@localhost" has been working but only internally; can't seem to get external mail in there. Is it possible to receive mail like this? Thanks.

You need to register a domain, and then setup its DNS records (in particular, its MX records) to point to your server machine. That way, when an email is destined for any "@yourdomain" address by any sending service, it will be routed to your server machine (which needs to run an SMTP server to receive emails - POP3 is for downloading emails from your mailbox, not for putting emails into it). If your server does not have a static IP, then you need to use a service like DynDNS to mange the DNS records for you so they can account for your dynamic IP whenever it changes.

"The Internet" doesn't use POP3 to send and receive email, it uses SMTP. Here's how email "flows" from the sending computer to the receiving computer:

Server needs to send email to address: myhome@localhost. The first thing it does is isolate the server name, that's the part after "@". Next it uses DNS to lookup the SERVER IP for the computer that's supposed to receive email for the given domain. DNS contains a special record for this purpose, it's called the "MX" record. You can use command line tools like dig on Linux or nslookup on Windows to find this address, or you can use an online tool like the one found at http://www.mxtoolbox.com/ (google found this site, I assume there are many others!).

If you try to locate the MX record for your "localhost" domain you'll obviously discover it's not possible, because it's not a fully-qualified name. You first need to get yourself an domain name, so you can register a MX record!

Things you need in order to RECEIVE email

1. Need an "real" IP address. Servers outside your local network need to contact your server, and they obviously need a way to do it. Make sure no routers along the way block SMTP ports.
2. You need to register an domain name, add a MX record and point it to your "real" IP address.
3. Need to run SMTP server software on your box. You can use Indy components to write one.

Things you need in order to SEND email

Theoretically sending email with SMTP is the easy part. You just contact the responsible server using SMTP and send email, that's the way the protocol works: any computer in the world may send email to any SMTP server.

Practically sending email is the most difficult thing you'd have to do, mostly because foreign SMTP servers don't trust you (ever heard of SPAM?). Here are some of the things you might need to do so foreign SMTP servers accept email from you. There's no definitive list because the protocol itself doesn't include a clear authentication mechanism, so every big SMTP server out there uses it's own heuristics to decide rather to accept email from you or not. You'll find yahoo especially fun!

1. You need to have REVERSE DNS for the IP you're using to send email.
2. You need to send from one of the SMTP servers listed in DNS as your MX servers.
3. Your DNS records need to have long TTL (this rules out Dynamic DNS services)
4. Many other things...

What people usually do?

eMail is hard, there's a surprisingly small number of full SMTP servers available for your own server: Exchange, Notes, Postfix, QMail, Sendmail. They're all notoriously difficult to configure. Most people would use hosted mail services, some people would use the SMTP services provided by the ISP, and very few would install one of the mentioned services.

If you really want to write your own SMTP server go ahead, but you might want to install one of the ready-made ones before, to get a bit of eMail and DNS experience. The Linux ones are cheap to install and may also help with development (you don't want to send too much bad email to your free yahoo address, you might get blacklisted!)

POP3 is a protocol to read email from a mailbox. The TidPOP3Server component implements a POP3 server (and AFAIK it has no host property to set...), while TidPOP3 implements a POP3 client. To read mail from GMail or any POP3 server you need a TidPOP3 component. The hostname to set is the DNS name the service instructs you to use (i.e. pop3.mydomain.com).