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Exchange 2003 SMTP not connecting on clients - POP is working

Tags:
  • Exchange
  • Exchange 2003
  • Exchange Server
  • SMTP
  • Servers
  • Business Computing
Last response: in Business Computing
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May 29, 2014 5:26:37 PM

I am a new administrator to a Server 2003 setup with Exchange Server with SP2. I am not sure how to phrase the questions, to help you help me. I am able to download messages via POP to an Outlook Client or Iphone, but when it comes to sending from an external client I get errors that say I cannot connect. I have tried changing settings in the client and in the Exchange System manager without success. We are not using SSL and I can send from internal clients no problem. If any additional information is need please let me know.
Thank You
Lawrence

More about : exchange 2003 smtp connecting clients pop working

May 30, 2014 10:40:30 AM

I would check and see if port 25 is being blocked see if you and telnet to it using port 25. Was SMTP working prior to you starting, was there any change after you started as the administrator.
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May 30, 2014 3:38:54 PM

Thanks Jeff
Port 25 is open, was able to telnet from the server but not remotely. Is there a good guide that is easy to understand out there that explains how exchange works. I am winging it now and being an older system there seems to be lots of information out there but nothing difinitive.
The weird part is now it seems like it is working to my Iphone and Ipad but not a remote outlook client. There are no settings I can tell that are different between the thre..
Thanks again
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May 30, 2014 6:40:23 PM

Most ISP's (the good ones anyway) block port 25 connections to anything but their own mail servers as a spam prevention method.
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May 31, 2014 9:36:54 AM

I ran the MX lookup super tool to see what ports are open on the external ip, I show 25, 80 and 110 as succesful so I have ruled it out. I have been successful a couple of times but the majority of times I get an error saying the server is not responding when trying to send email. I would think it is a server error but not sure what settings need to be changed. We do not have an SSL certificate how important is that?
Thank You
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June 3, 2014 5:39:51 AM

What you can try is use MXTOOLBOX and run the test email server. You want to use either your WAN IP or email domain name. See if that passes. I do agree with ex_bubblehead about most ISP's blocking port 25 I know I have ran into that problem with ATT. You might be able to switch it so SMTP uses 587 instead of 25. But give your ISP a call and see if they are blocking port 25.
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June 5, 2014 2:37:52 PM

This sounds like a relaying problem. By default, Exchange 2003 is set up to deny relaying from IP addresses outside of your local network. This prevents other mail servers from using your server to send spam and such. Since your external clients are connecting through a different ISP (such as a wireless hot spot), any requests to send are sent first to the ISP they are connected to and then relayed to your server. Your server denies these connections by default.

You will need to set up your SMTP Receive connector to accept connections from any IP address in order to make this work. Be sure and set up authentication for these connections, though, as you don't want anyone but your own users to be able to connect and send mail through your server.
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June 8, 2014 2:00:38 PM

Jeff - ran the tools got this error -
We were able to connect to your mail server on port 25 and complete some test commands, but SMTP session took much longer than expected. This could indicate that your email server is under heavy load.

Not sure what type of tests to run to see if this is the case. Ran on a Sunday with no one accessing server.

Derek - thanks for the input I will look into the SMTP Receive connector.
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