Re: port 587

[Matt Simpson <net-qmlist@jmatt.net>]

At 2:16 PM 3/8/07, Mario Salazar Baños wrote:
> I have a question, could be used to spam this port?
Any port accepting SMTP traffic can be spammed if 
you don't take adequate precautions.
>  or what is the benefit of use this port?
Well, technically, you can use it for anything 
you want.  But its conventional use is an SMTP 
server used only to relay outbound mail from your 
clients.  The benefit of this is that it 
separates your outbound traffic from the inbound 
traffic on port 25.  It also allows your clients 
to relay mail through your server even if they 
are connecting through an ISP which blocks 
outbound port 25, which is becoming more common.
This allows you to use different control 
techniques on the different ports.  For example, 
you could (and probably should) require any 
client connecting to port 587 to authenticate. 
You would probably not want to have such a 
restriction on port 25, unless you have some very 
unusual requirements for inbound mail.
If you require authentication on port 587, then 
you can eliminate some other spam control 
techniques that you might use on port 25 (such as 
RBL), if they are causing problems for your 
clients.  If the client has authenticated, then 
you know you want to accept mail from him, even 
if he's in an IP block which has been accused of 
spamming.