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¿magic using port 465?

February 20, 2011 at 07:54:05
Specs: Windows 7
Hello everybody. I have a doubt about mail servers working on port 465 (for example or
I try to connect using for example: "telnet 25"
There's no problem. The connection is established. But if I use wireshark to analize the connection I get and unexpected result:
The TCP packet corresponding to the command "telnet 25" has the value 465 into the field destination port. I expected to find the value 25 in this field. How is this possible?. Who has said to my computer that the destination port is 465 instead 25?.

Thank you for your help.

See More: ¿magic using port 465?

February 20, 2011 at 08:24:43
Your telnet is going to the simple smtp port, 25. Your mail program must be configured to used secure smtp:

POP3 - port 110
IMAP - port 143
SMTP - port 25
HTTP - port 80
Secure SMTP (SSMTP) - port 465
Secure IMAP (IMAP4-SSL) - port 585
IMAP4 over SSL (IMAPS) - port 993
Secure POP3 (SSL-POP) - port 995

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February 20, 2011 at 08:58:03
Paul1149 thank you for your answer, but I don´t want to configure a mail program. I just want to know how is posible that my computer use port 465 if I have indicate to use port number 25. How does my local machine know this port (465). I didn´t indicate to use this port (465) at any moment.
Than you.

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February 20, 2011 at 09:09:17
I see. I didn't realize that the 465 packet was from telnet. Not sure how that would happen, unless somehow the mail server redirects 25 to 465.

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Related Solutions

February 20, 2011 at 09:48:18
Hello. There's no mail server redirection. Take a look: this is a screen capture of the traffic in my computer when I execute telnet through port 25. Exactly when I execute telnet, frame number 10 is sent (this frame is described in this image). As you can see the port used is port number 465 (not 25).


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February 20, 2011 at 10:58:38
Take a look HERE for "URD Host Signaling". My port info on 465 was legacy, and some sort of switching is now done by the final router in the route using this port. I'd be interested in what that Wireshark output reads in that expansion point in the details, immediately before the 465 mention.

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February 20, 2011 at 13:22:43
Hello. I think that there's no relation with urd but I suspect that maybe you're right when you say that the final router is changing something. If you are interested in the dialog captured by wireshark you can download it from here. It's a file which can be opened using wireshark (I use version 1.4.3). In the file, telnet command begins in frame number 4.
Thank you for your time

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June 8, 2011 at 02:42:17

I encountered the same problem. Avast antivirus was the cause. If you disable avast antivirus and disable mail shield it will be connecting to port 25 instead of 465.


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June 8, 2011 at 12:52:53
465 is for smtp over ssl
465 is the distination port not a local port

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