nanog mailing list archives
Re: Why do so few mail providers support Port 587?
From: Nils Ketelsen <nils.ketelsen () kuehne-nagel com>
Date: Mon, 28 Feb 2005 16:54:23 -0500
On Sat, Feb 26, 2005 at 03:10:42PM +0100, JP Velders wrote:
From a "security" stance (well - partly ;D) I always like to emphasizethat in "The Real World" port 25 is for traffic between MTA's *and* submission of mails to the local MTA. So to reduce the chance of one of my users abusing an Open Relay and to enforce corporate e-mail policies, only port 25 towards our mailserver is open.
I do not know about your E-Mail Policy, but normally it is either allowed to use an external mailserver or not. If it is allowed, I can as well allow Port 25 outgoing. If it is not I will block 25 and 587.
Port 587 on the other hand is meant for "submission" by clients. The security implications of allowing my users to contact such a port are very very low. If someone won't secure his mailserver on port 587, that's something different, but substantially different than if it were insecure on port 25...
An interesting theory. What is the substantial difference? For me the security implications of "allowing the user to bypass our mailsystem on port 25" and ""allowing the user to bypass our mailsystem on port 587" are not as obvious as they maybe are to you. Nils
Current thread:
- Re: Why do so few mail providers support Port 587? Michael . Dillon (Feb 28)
- <Possible follow-ups>
- RE: Why do so few mail providers support Port 587? Michael . Dillon (Feb 28)
- Re: Why do so few mail providers support Port 587? Steven M. Bellovin (Feb 28)
- Re: Why do so few mail providers support Port 587? Nils Ketelsen (Feb 28)
- Re: Why do so few mail providers support Port 587? Valdis . Kletnieks (Feb 28)
- Re: Why do so few mail providers support Port 587? Nils Ketelsen (Mar 01)
- Re: Why do so few mail providers support Port 587? Frank Louwers (Mar 01)
- Re: Why do so few mail providers support Port 587? Nils Ketelsen (Mar 01)
- Re: Why do so few mail providers support Port 587? Valdis . Kletnieks (Mar 01)
- Re: Why do so few mail providers support Port 587? Valdis . Kletnieks (Feb 28)
- Re: Why do so few mail providers support Port 587? Valdis . Kletnieks (Mar 01)
- Re: Why do so few mail providers support Port 587? Michael G (Mar 01)
- Re: Why do so few mail providers support Port 587? Jason Frisvold (Mar 01)
- Re: Why do so few mail providers support Port 587? David Lesher (Mar 01)
- Re: Why do so few mail providers support Port 587? Chris Horry (Mar 01)