LIME St. Lucia SMTP Blocking - End User Edition

By: Jason Hynds
Site: http://jsun4it.blogspot.com
Date: 2009-09-14


LIME St. Lucia was discovered to be one of the sites for a hush hush change in network policy that blocks persons from sending e-mail through third party E-mail Service Providers (ESP) using SMTP (Simple Mail Transfer Protocol) on TCP (Transmission Control Port) port 25.

LIME St. Lucia (http://www.time4lime.com) has not issued any on-line alerts on this change in policy. Checks were made up to September 12th, 2009 on their Service Alerts web page - which was empty, and also with other informational pages such as Press Releases and Promotions.

This network policy changes apparently intends to combat spam from originating on the LIME network, especially from subscribers with infected computers commonly called zombies. These zombie computers can act as a spam sources by mimicking the functionality of mail servers. Such spamming computers can utilize significant network bandwidth and cause spammed destinations to complain to and for the customers' Internet Service Provider (ISP).

Unfortunately the same SMTP on port 25 is popularly used for legitimate business communication. Particularly those end users and businesses utilizing third party ESPs are expected to be affected by this policy change. It is suspected those using LIME St. Lucia as their ESP remain unaffected, but this has not been confirmed. This possibility however raises the question of if this action can be considered an anti-competitive business practice, especially since the choice of Internet Service Providers (ISP) is limited, and most local and regional ESPs are likely to be considerably smaller and less technically resourced than LIME.

This network policy change may have resulted in multi-day and multi-week outages for some customers and shaken their confidence in their otherwise innocent ESPs. Some affected LIME clients have been notably peeved at what has been seen as the lack of proper notice from LIME.

The network policy change is known to affect ADSL (Asynchronous Digital Subscriber Line) subscribers. It is however possible that, at least on initial roll-out, leased line customers were also affected. This change in policy appears to be 2 to 3 weeks old at the time of publication.

For ADSL subscribers looking to resolve this issue, LIME states they must first migrate to a premium business package, at additional cost - if not already on one. Perhaps at no additional cost the customer can use LIME St. Lucia as a smart host - as this is the standard practice by ISPs who implement this policy.

The SMTP protocol on port 25 has traditionally been used for both:

1. sending e-mail messages between end-user e-mail client software (such as Microsoft Outlook, Mozilla Thunderbird and Eudora) and mail servers - a process known as message submission and,
   
2. for sending e-mail between source and destination e-mail servers - a process called message relaying.

The actual correct solution to resolve a problem in message submission is for the customer and their ESP to utilize message submission on port 587, instead of port 25, as described in RFC 4409 (http://tools.ietf.org/html/rfc4409). LIME St. Lucia does not block this port. By applying this solution, the customer is neither coerced into paying LIME St. Lucia more money in order to workaround its silent change in network policy nor does he/she have to introduce LIME's mail servers into the process of message delivery (thus separating technical support responsibility for mail issues based on if messages are being sent or received).

To resolve an issue with message relaying - where a publicly accessible mail server is operated on-site, is may be necessary to request a site exception to this policy from LIME St. Lucia.

If further silence comes from LIME on this issue, other jurisdictions should probably brace for similar policy changes.