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SMTP server "mail.dmzz.biz" is not responding

Posted on 2011-02-22
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Last Modified: 2012-05-11
I have a problem, which I think has a simple solution, but I have been at it for 2 weeks now and I just can't seem to correct it.
I'm running Snow Leopard Server on a Mac Mini v.10.6.6
The server is up and running correctly and for a router I'm using a Time Machine.
as far as the internet and intranet all is working correctly. On the Time Machine I have port 25(SMTP) 110(POP) & 143(IMAP) open, but when I try to setup any e-mail client or on my iPhone I get an SMTP server "mail.dmzz.biz" is not responding or sometimes an POP server "mail.dmzz.biz" is not responding. I have rebuild my DNS, rebuild Open Directory, my ISP created a PRT Record to point to my static IP address which I can check on MXTOOLBOX.com.
Network Solutions is hosting my domain and I created an A Record to point to my static IP as
mail.dmzz.biz and an MX record. all is pointing correctly. But still I can't connect.

Any ideas I what else I can check?

Thanks for all of your help.
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Question by:noad
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by:woolnoir
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Did you setup a port forward for port 25 on the router to your OSX server ?

you said that the port is 'open' but not that its forwarded.
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by:woolnoir
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Same with 110 and 143 are they forwarded to the OSX server
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by:woolnoir
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mail.dmzz.biz is responding on port 21 (ftp).
mail.dmzz.biz is responding on port 22 (ssh).
mail.dmzz.biz isn't responding on port 23 (telnet).
mail.dmzz.biz isn't responding on port 24 (lmtp).
mail.dmzz.biz isn't responding on port 25 (smtp).

mail.dmzz.biz is responding on port 110 (pop3).

mail.dmzz.biz is responding on port 143 (imap).

imap and pop3 looks to be responding at least.
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by:noad
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Yes, the ports are forward on the router...
25 to internal ( srv ) static IP, same for 110 & 143.
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by:woolnoir
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can you telnet to your server port 25 internally and type HELO do you get any response ?
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by:noad
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not very good with telnet can you explain how I should do it?
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by:woolnoir
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open a cmd prompt in windows, or a terminal in OSX /applications/utilities and type 'telnet server 25' obviously server is your internal oSx server IP.
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by:noad
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when I ping mail.dmzz.biz it points to the correct static IP and enclosed is a snap shoot of the telnet out put  

Screen-shot-2011-02-22-at-3.17.0.jpg
ping-mail.dmzz.biz2011-02-22-at-.png
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by:noad
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Are the above not correct?
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by:woolnoir
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ok it is working inside then. But the port isnt open from the outside so the port forward isnt working correctly. Can you show me a screenshot of the port forward in the timecapsule interface for port 25.
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by:woolnoir
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pinging mail.dmzz.biz works yeah, but telnetting to the external interface on port 25 i.e telnet mail.dmzz.biz 25 does that work ?
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by:noad
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one sec, will send now
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by:noad
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by:noad
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is that what you wanted to see?
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by:woolnoir
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that is what i wanted, and you appear to have it configured correctly...mmm *thinks*
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by:noad
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Driving me crazy.....
Only thing I can think of is to reset the ( router ) Time Machine to it's factory defaults and reconfig and reopen the ports.
I spoke with ATT and they assure me that they are not blocking port 25.

Ideas???
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by:woolnoir
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ARGH... i would check that .. because AT&T very often block 25...

I have a method to check for you...

Add a new port forward, public TCP post 3456, internal port TCP 25, IP address of your internal server.

If the above works (either of us can test) it will prove if AT&T are blocking port 25 for you.
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by:woolnoir
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small typo i meant ' Add a new port forward, public TCP port 3456, internal port TCP 25, IP address of your internal server.'
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by:noad
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Not sure I follow?

explain...
if I understand you, you want me to open port 3456 public and point it to port 25 private?
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by:woolnoir
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make a new port forward on external port 3456 (TCP) and point it to your server at post 25 TCP

if this works, as in if i can connect to it, it will mean AT&T are blocking port 25 for you... as the port forward will be exactly the same as the one you already have, apart from instead of being on port 25 externally, it will be 3456.
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by:woolnoir
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So call it SMTPMAIL2

PUBLIC TCP PORT 3456
PRIVATE IP 192.68.1.50
PRIVATE TCP PORT 25
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by:woolnoir
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I can connect on port 3456 and get a SMTP response so it looks like AT&T are blocking port 25 unfortunately
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by:woolnoir
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cmd
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by:noad
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by:woolnoir
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Yep and it works see above screenshot... it means AT&T are blocking port 25 for you... :(
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by:noad
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So I was right,  those AH LOL
can't trust anyone.
so until port 25 is unblocked by ATT I can't connect.
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by:woolnoir
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Yep thats about it... imap and pop3 appear to be open though, so they should work. I can connect to port 110 TCP and get a dovecot prompt so that works.
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by:woolnoir
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An alternative is to use a service like http://www.changeip.com/email/dspBackupOverview.asp

what they do is you pay them to run a SMTP server for you on port 25... so your domain would have

smtpblahblah.changeip.com MX 10

they would accept your mail and forward it onto a port at your server other than 25, say 3456 which would allow you to accept mail.

Or you can demand AT&T sort their block out...
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by:noad
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Awsome, I'll call ATT again.

what Telnet command so I use to check from here, I'm outside of the network?
in other words can you show me the telnet command that you used? PLZ
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telnet mail.dmzz.biz 3456    <-- that tests the new port forward we added
telnet mail.dmzz.biz 25 <-- that tests the one that should work which AT&T are blocking
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by:noad
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 Thank you for all of your help!
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by:woolnoir
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always a pleasure :)
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by:noad
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Very simple to work with, explained things in a simple easy way to follow.
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