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SMTP Relaying - 2 Questions [message #1395] Sat, 25 February 2006 18:40
Geforce
Messages: 8
Registered: February 2006
Junior Member
After much playing about and reading the manual, I've finally decided to post here, so let's see what you guys can tell me!

I've got two questions, which are pretty simple so I'll fire away!

1) My network is set up simply, with a firewall that acts as the mailgate, the smarthost that acts as my NST relay, and a mailserver which is umm, my mailserver!
So, incoming is pop3.demon.co.uk > Firewall > Smarthost > Internal Mailserver.

However, when I set the mailserver to pass mail "back" through the smarthost (running NST), it always gets blocked and the sender receives a fatal error message after approx 30 seconds, so I've skipped out the smarthost in Outlook/Outlook Express's settings so it goes :

Outgoing mail: Mailserver > Firewall > smtp.demon.co.uk

There are two downfalls with this - 1 is that the user can see the mail "sending" for a long period of time, instead of it being instantly sending it to the Internal Mailserver.
2. Anything over around 4mb, and the user always recieves the Outlook error "wait 60 seconds for the SMTP server to respond" or something..

Any ideas?

2) Can NST Relay mail to more than one Mailserver on different domains? (obviously with 2 network cards in the system)

If so, how to both of them questions?

Much appreciated if someone can respond.

Ps. NST is running on a Windows 2000 Pro box. It's a PIII 850mhz with 256mb Ram and works great!

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Edit:

I've been reading through other posts, and I came across a similar problem. My mailserver is running "SLMail" by Seattlelabs. The options I have turned ON are:

Broadcast ESMTP size
Disable MX Lookup
Do EXPND VRFY
Use Built-in router
Use ESMTP Protocol
Use ESMTP Size
Use Four digit year
Use Message from field

There is definately no setting within the SLMail Administrator to verify incoming hosts. NST does say "If you put *@yourdomain.com in this box, then NST will NOT relay outgoing mails" - But if I turn this option OFF, then I'm open to the world?

So, I need to upgrade my Mailserver software?
------------------------------------------------------------------------------------------------------------------------
Regards,

Ian Harris.



Post Edited (02-26-06 02:52)
Re: SMTP Relaying - 2 Questions [message #1396 is a reply to message #1395] Sun, 26 February 2006 18:18 Go to previous message
Heidner
Messages: 121
Registered: February 2005
Senior Member
As far as I know NST is only supposed to check incoming mail and not outgoing mail also.

NST doesn't have a mail queueing mechanism... so if even if it could relay your out going mail.. if there is a delay contacting the external emtp server - it would also be impacted.

Are you using IMAP4 internally between clients, smtp between internal clients or POP3? If smtp - did you remember to change the internal smtp clients to the same port that you changed slmail -- after you installed NST. I.E. something like port 26 for slmail....
Re: SMTP Relaying - 2 Questions [message #1397 is a reply to message #1396] Sun, 26 February 2006 18:24 Go to previous message
Geforce
Messages: 8
Registered: February 2006
Junior Member
The mail doesn't even get as far as passing through NST outgoing.
I can see in NST that it says "example@mydomain" is rejected.
After a number of attempts, the mail is bounced back to the sender with "Fatal error 8192 bytes blah blah blah"

SMTP between clients.

Outgoing mail is set to Port 25 in Outlook, and 25 also in SLMail - Why would it be a port issue?

The mail gets as far as NST and then is bounced back, hence me using the firewall as the external gateway for mail instead of the Internal Mailserver.

------------------------------------------------------------------------------------------------------------------------

Edit:

I feel this is more an SLMail problem rather than NST.

Before I used NST, I was using ClearSwift MAILsweeper, but version 4.x is really poor, hence me upgrading to NST.

I think I'll look into updating SLMail to Exchange.

If someone from support can verify that SLMail is the problem, then I'll be happy Smile

------------------------------------------------------------------------------------------------------------------------

Regards,

Ian Harris.



Post Edited (02-26-06 18:29)
Re: SMTP Relaying - 2 Questions [message #1398 is a reply to message #1395] Sun, 26 February 2006 20:31 Go to previous message
Heidner
Messages: 121
Registered: February 2005
Senior Member
The port issue is because -- NST is designed to listen on port 25 (smtp) and accept ALL incoming traffic. It then routes the mail out to the IP device on the which ever port you specify typically port 25 (as specified in "mail server" on the first screen of the general mail setup).

If you are pointing the outlook clients to the NST machine... and you have left their ports set at port 25.. any mail they send will be directed back into the NST machine - which would then forward it to the mail server -- creating a loop.

Instead the mailserver should be setup to send outgoing mail to the external smtp machine only. Typically you want to specify that the mailserver accepts mail from some other port than 25 -- that way hackers and spammers can't somehow bypass the NST box and get to your mailserver. Let NST accept all incoming port 25 traffic and forward to the mailserver.
Re: SMTP Relaying - 2 Questions [message #1399 is a reply to message #1398] Sun, 26 February 2006 21:47 Go to previous message
Geforce
Messages: 8
Registered: February 2006
Junior Member
I am NOT pointing the mail clients to the NST box. (This is smarthost.mydomain.local)

I am pointing (currently) my mail clients to my FIREWALL that uploads to the SMTP server which is firewall.mydomain.local

I want to point my mail clients at my INTERNAL mailserver which is mailserver.mydomain.local but can't - because for some reason the mailsever requires mail to be relayed BACK THROUGH smarthost.mydomain.local. It will NOT relay mail directly to the firewall.mydomain.local

But like I said, doing that causes the mail clients to possibly timeout, sending mail directly to the upstream SMTP server of my ISP.

I want mail users to send mail directly to the internal mailserver that relays mail through the NST box which then passes it back through the firewall to my ISP's SMTP server.

However, like I said, I'm starting to think that this is more of a mailserver issue rather than that of the NST box.



Post Edited (02-26-06 21:52)
Re: SMTP Relaying - 2 Questions [message #1400 is a reply to message #1399] Sun, 26 February 2006 21:50 Go to previous message
Geforce
Messages: 8
Registered: February 2006
Junior Member
If this does turn out to be a problem with my mailserver software, and not just some configuration that I've not set up correctly in NST, then I guess it renders my second question absolutely useless Smile



Post Edited (02-26-06 21:51)
Re: SMTP Relaying - 2 Questions [message #1401 is a reply to message #1399] Wed, 01 March 2006 00:56 Go to previous message
Heidner
Messages: 121
Registered: February 2005
Senior Member
>>I want mail users to send mail directly to the internal mailserver that relays mail through the NST box which then passes it back through the firewall to my ISP's SMTP server.

I'm pretty sure this will never work. NST will not relay it outbound -- only inbound to your mailserver.

>>I want to point my mail clients at my INTERNAL mailserver which is mailserver.mydomain.local but can't - because for some reason the mailsever requires mail to be relayed BACK THROUGH

Hard to say what is causing this - without more detailed error messages from the servers and clients. But my wild guess is that mailserver thinks that you are trying to illegally relay mail through it. You may need to change some setting on the mailserver.mydomain.local to allow any box in *.mydomain.local to send it mail.

You could also explictly tell SLMAIL to accept mail from a box by specifying an range of IP addresses that SLMAIL will accept.

Other items that could cause a problem ... if you configured slmail with an internet domain of "mailserver.mydomain.local" instead of "mydomain.local" ... or if the other PC's are running win2k+ and do not have the same domain as part of their network name.

Finally when configuring multiple filters and mailers.... the smtp services is often moved to a different port number... it might be that you are trying to send mail on port 25 to a box that the smtp port number was switch to 26....
Re: SMTP Relaying - 2 Questions [message #1402 is a reply to message #1395] Wed, 01 March 2006 21:09 Go to previous message
Geforce
Messages: 8
Registered: February 2006
Junior Member
Yeah, cheers for the info. Got some ideas in mind to try.

I fear I've just got outdated mailserver software because it seems to HAVE TO relay to some sort of "smarthost" before it sends it externally from our network.

I downloaded the PDF manual this evening (195 pages) for some light reading later on..

Maybe they do a digest version?

Haha.. keep on dreaming Ian!

Thanks for the input, much appreciated.

Ian.
Re: SMTP Relaying - 2 Questions [message #1403 is a reply to message #1401] Thu, 02 March 2006 23:44 Go to previous message
Geforce
Messages: 8
Registered: February 2006
Junior Member
I have now managed to solve the problem I was having.

After going about such problem. I now understand a lot more about SMTP/Proxies etc..

Thank you very much for your help within this matter.

Best Regards,

Ian Harris.
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