-3

I installed hMailServer on Windows Server 2003 and somehow I can't connect to SMTP 25 port from all computers. When I run the following command, it connects successfully on some clients, but on others it doesn't.

telnet myhost.com 25

I have added an exception to the Windows Firewall for 25 port, but this does not seem to help.

MDMarra
  • 100,734
  • 32
  • 197
  • 329
ihorko
  • 155
  • 1
  • 1
  • 9
  • Any local firewall installed on the workstations? – Vick Vega Dec 12 '11 at 20:25
  • I turned off firewall but it still doesn't connect. – ihorko Dec 12 '11 at 20:30
  • 3
    Are you using an antivirus on these clients (I hope you are)? Some of them (notably MCAfee) block outgoing SMTP connections hoping to deter worms. – Massimo Dec 12 '11 at 20:36
  • Yes, I have, but why it doesn't block for all requests? – ihorko Dec 12 '11 at 20:39
  • 4
    @ihorko - you have failed to answer the most basic question required for anyone to assist you in troubleshooting: ***What is different between the working machine and the non-working one?*** (Network/Location? Software installed? Settings? etc.?) – voretaq7 Dec 12 '11 at 21:21
  • 3
    And the Lord spake from on high and proclaimed **"Thou shalt use a sniffer to see what is failing."** – Zoredache Dec 12 '11 at 21:22
  • I do not understand why this question was voted down. Those of us who administrate SMTP servers knows very well that many ISPs blocks port 25 by default (and that is a good idea, assuming that there is a way to remove the block). This was my very first thought when I read the question. On the other hand it is a complete mystery for a newcomer, who are accustomed to a completely open internet. It is strange that nobody answered the question immediately. There is no need for further investigation to give a good guess here, the comments were not really helpful. – Hontvári Levente Dec 13 '11 at 03:05
  • @HontváriJózsefLevente nowhere does he mention that he is testing from outside his LAN or that there are clients at remote sites, etc. He has put minimal effort into trying to help himself or provide in-depth detail, so the question gets downvote. – MDMarra Dec 14 '11 at 02:42

3 Answers3

2

If people want to send mail on port 25, they should be connecting to their mail server, not yours. Port 25 is still occasionally used for internal mail submission, though it really shouldn't be. But it's primarily for one mail server to contact another for inter-domain mail relaying.

Why are ordinary users trying to connect to connect to your mail server on port 25? Port 587 is for remote mail submission.

David Schwartz
  • 31,449
  • 2
  • 55
  • 84
1

You've given little detail, so any answer is just a stab in the dark. That said, here's mine:

If it's not blocked by a firewall ACL, it's probably blocked by anti-malware. McAfee labels this "Prevent Mass Mailing Worms from Sending Mail" in the Access Protection section. Chances are, other AVs have a similar configurable setting.

MDMarra
  • 100,734
  • 32
  • 197
  • 329
  • Yes, I have Comodo Antivirus, but why it doesn't block all requests – ihorko Dec 12 '11 at 20:41
  • I'm not saying with any certainty that it's your antivirus, but it's possible that it's configured differently on some workstations. Really, you haven't provided enough details for anyone to make any real educated guesses. – MDMarra Dec 12 '11 at 20:43
  • Ok, what details you need? I don't know what details should I provide – ihorko Dec 12 '11 at 20:46
  • @ihorko Any relevant log entries, procmon or netmon traces, you know...the troubleshooting that you should have done before you asked the question. – MDMarra Dec 12 '11 at 20:47
  • on localhost everything works perfect, or you mean run netmon on pc's where I can connect? – ihorko Dec 12 '11 at 21:01
  • @ihorko You're asking extremely basic troubleshooting questions right now. That's really not something that I'm willing to hold your hand through. Sorry. – MDMarra Dec 12 '11 at 21:02
1

I figured out. It's because on pc's where it doesn't connect, ISP blocks 25 port

ihorko
  • 155
  • 1
  • 1
  • 9
  • 3
    This is an ***incredibly*** common situation in the modern world. There is even a whole separate RFC (http://tools.ietf.org/html/rfc2476) & port (587) for handling this :-) – voretaq7 Dec 12 '11 at 22:25
  • There is no reason an ordinary user should *ever* be connecting to your mail server on port 25. Port 25 is for one mail server to connect to another mail server with which it has no previous arrangements. – David Schwartz Dec 13 '11 at 02:23