just forwarding reply from smartelecom (read the text below or click the link:
http://support.smarttelecom.ie/forum...ad.php?t=159):
Administrator
Join Date: Aug 2005
Posts: 8
Default Blocking outbound SMTP(TCP port 25)
This block has now been implemented - 23/1/2006
This block has been modified to permit outbound port 25 access to business customers by default - 24/1/2006
As our DSL user network has grown we've been receiving an increasing number of complaints about SPAM coming from DSL user machines.
This SPAM wastes peoples time and network/computer resources. It also leads to problems for all DSL users because it increases the chances of valid emails being rejected as more of our IPs appear in email blacklists.
So, for the above reasons amongst others, we have decided to start blocking outbound SMTP(TCP port 25) traffic from DSL users with dynamic IPs. Customers with static IPs will have the option of requesting the opening of outbound SMTP for their static IPs.
This will no negative effect on the vast majority of users. However, if you are currently using an alternative outbound SMTP mail server you will have to change this to:
smtp.mysmart.ie
as described in the mail guide.
This change will come into effect from Monday January 23rd.
We're far from the first to do this, heres some backround reading if you are curious:
http://www.dslreports.com/shownews/38004 http://www.eweek.com/article2/0,1895,1784276,00.asp