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Change SMTP from 25 to 587

Posted on 2010-08-25
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Last Modified: 2013-11-30
I have a two part question:
re: Small Business Server 2003 using exchange 2003

To avoid BOTs and Trojans It's been recommended that port 25 be closed completely and that port 587 be set as the SMTP port.

I know i can change the port by going to Exh System Manager, Server, Protocols, SMTP and properties of Default SMTP VIrtual Server.   However I"ve read that changing from 25 to 587 may cause a problem unless 587 is set to listen.  Also I've read that a certificate is needed on 587.

Question 1:  what is the best way to implement the change to port 587 from port 25.   How does one make 587 listen and how does one install a certificate on a port?
Question 2:  how can I then shut down all access via port 25  (thru routing table on router?)

Thanks
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Question by:bborner
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by:Will Szymkowski
ID: 33527406
Q1. Take a look here as MS illustrates the best way to configure this.
http://support.microsoft.com/kb/274842

Q2. You can block port 25 using your corporate firewall appliance. This would be the most effective way to accomplish this.
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by:panman3
ID: 33531913
If I'm not mistaken then you are mentioning the port used by external client software and not the one used by your server to accept mail so:

configure the SMTP virtual server to use port 587 AND with authentication enabled (=> "internal" users using the SMTP servers with their mailclient; f.e. POP users that need an SMTP relay server).
make sure port 25 stays open on your firewall because this is used for external to internal mail (f.e. me as an external contact sending an email to your address)

But you are correct that port 25 is not to be used for relaying and should not be used on the SMTP-relay-service! Only for accepting and sending mails to/from your internal mailboxes.

Regards,
Geert
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panman3 earned 500 total points
ID: 33532032
I checked:
you need indeed 2 (!!!) different receive connectors:
- 1 default connector for accepting external mails (typically called "default internal receive connector <servername>")
- 1 client connector for your mailclients to relay (typically called "Client <servername>")

The tutorial mentioned by Spec01 is only for changing the default connector if you want intra-site-communication (f.e. exchange servers 1 at location A needs to connect to server 2 at location B and does so over a different port than 25; server 1 accepts mail on port 25, server 2 does not; 1 relays mails that are for server 2 via port xxx). There still needs to be a connector on port 25 somewhere that can accept incoming mail from external parties.

Regards,
Geert
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