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suddenly, i can't send e-mail

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by iphicles 1 view

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I'm running Exchange 5.5 with outlook 2000. my LAN exchange clients can send/receive fine. My remote internet clients, those who use other ISP's to access the Internet, can receive pop3 e-mail from my exchange server, but none of them can send e-mail. This just started happening a few days ago. Here's an ex:
laptop user running win2k/outlook 2000/earthlink isp. pop3/smtp servers are our exchange server. i can receive, but can't send. when i change the smtp server to any other (eg: earthlink, yahoo, etc...) it works. again, my LAN exchange clients can send, but my remote can't. any ideas?
p.s. the error i get is "the server was found, but there was no response..." and "unable to connect to the outgoing mail server (SMTP). Please verify the server name...."

5 replies

by xiaxiong

This could be an ISP / Security issue. For instance, you may have had an open relay, which allows anyone to send email from your server. If this is the case it is just a matter of time before some spammer finds it and starts sending thousands of spam messages from your server. Should this happen, your ISP will become aware of it fairly quickly, and will take measures to stop it, which may include blocking your SMTP port. Often they will not get around to telling you they did this. So firstI would check with your ISP.

Of course, it could also be a firewall / proxy issue, or a configuration issue with your server...

HTH...

by iphicles

Thanks! I spoke with the ISP's techs and they told me that they block all traffic on port 110 except to their server. It was their fault.

by dynamo2003

This seems like a DNS relay problem. Check to make sure that messages can be routed to your ISP using the correct DNS and MX record on the side of your ISP. Do a trace route to your ISP and make sure that DNS is working correctly with your mail server's IP address.

by iphicles

yeah, my pop server and smtp server are the same. checked name resolution, etc. but it turns out I was being blocked by the ISP's. Thanks anyways.

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