Accept All Incoming Email Messages on Server

I want to write some email scanning software and don't understand how to setup my server. I have a hosted web server running Windows 2003 Server. It is running the Default SMTP Virtual Server with a fully-qualified domain name of abcdef.com (example). DNS is pointing abcdef.com to my server. If I spoof an email from my desktop pc so that it appears to come from info@abcdef.com, and I send the email to a 'non-existant' email address then the bounceback does arrive on my web server and is stored in C:\inetpub\mailroot\Queue on the server - great! (I can scan it and handle the bounceback). However, if I simply send an email straight to info@abcdef.com then it does not seem to get placed anywhere on the server. I don't understand why bouncebacks get stored but开发者_StackOverflow other incoming email doesn't. I'm keen to avoid having to install any 'email server software' on the server, as I want to keep things as clean as possible. All I really want is some way of telling the server to accept all incoming messages to abcdef.com so that I can process them myself, and to place the .eml files in a known directory that I can scan. I'll then write an eml file parser to process the files. Thanks very much.

A possible reason for the lack of delivery is that your domain has a DNS A record, but no DNS MX record. MX records are used for delivery of mail. Historically, if no MX record was present for a domain, mail servers were supposed to fall back to looking for a domain's A record.

In your case, I'd guess that your local mail-sending software is looking for an MX record and then stopping if it doesn't find one, whereas the remote system sending you the bounce is looking for the MX record and then looking for an A record when it can't find one.

The Wikipedia article on MX records has more details.

SMTP is a message transfer agent (MTA), responsible only for handling the transfer of mail from one point (the client, perhaps) to another (the mailbox server, such as a POP or IMAP server). SMTP servers aren't the right tool for ultimately handling mail coming INTO a domain -- they only handle transferring the mail coming into a domain to another app, such as the aforementioned POP or IMAP server, which then know how to sort and store that mail.

In short, the Default SMTP Virtual Server isn't the tool you're looking for for your project.

From this other StackOverflow question, it looks like there are a few SMTP servers which are intended for development use but which might serve the purpose you seek -- they accept incoming messages and then write them to files (in some manner, and with some tweaking).

Ok, working now. Issues were as follows:

1. There was no MX record, so external email wasn't being directed to the server. The .EML file that existed on the server was indeed placed there by an outbound email process.
2. The firewall was blocking port 25 - now opened.
3. It is necessary to have some sort of inbound email service running on the server. Windows Server has a lightweight POP3 service which you can configure to place all incoming email into a single 'catch-all' mailbox. This fills with .EML files, which can then be scanned by our custom service.

Many thanks to delfuego & Jon.