Can't understand mail traffic principles

[Surfer]

Hello!
I have a Linux-based mail server in my LAN and Wingate on the ADSL access point. External clients (from Internet) connecting to Wingate and get resources from my LAN (FTP, http etc.). Everything seems to be ok.
But I can't understand how give them an ability to receive mail from my intranet mail server. I'm very satisfied by TCP and UDP mapping methods, but as I think they are not applicable for this type of traffic.
I can't find similar mechanism inside POP and SMTP proxy services of Wingate. I'm stuck. :(

[Pascal]

Have you tried the TCP mappings? They should work fine.

However, which version of WinGate are you using?

[Surfer]

Have you tried the TCP mappings? They should work fine.

Uhm. I must create two TCP mapping services, yes?
One working on port 25, binded to external. Mapped to my LAN server into port 25.
Second working on port 110, binded to external. Mapped to my LAN server into port 110.
And that's all. Must work, yes?
I'm just confused because think that POP and SMTP a bit more complex than ordinary TCP like WWW.

However, which version of WinGate are you using?

6.0.3 enterprise for 50 users.

[Pascal]

Correct in the setup. The protocol itself - well, the complexity is debatable. HTTP 1.1 (Full implementation, with chunking, etc.) is an interesting one too.

A TCP mapping is nothing more than a big pipe, however. The people who need to understand the protocol, your email client and your email server are on either end of that pipe.

Doesn't matter which protocol is going across it.

[Surfer]

Correct in the setup. The protocol itself - well, the complexity is debatable. HTTP 1.1 (Full implementation, with chunking, etc.) is an interesting one too.

A TCP mapping is nothing more than a big pipe, however. The people who need to understand the protocol, your email client and your email server are on either end of that pipe.

Doesn't matter which protocol is going across it.

Ok, I'll try this.
Thank you for support!