This page adds detail to the email configuration troubleshooting page for the following topics:
Most ISPs disallow outbound SMTP connections for their residential Internet access subscribers. This is a courtesy to the rest of the Internet: it limits the sending of spam by that ISP's own users.
The reasoning goes like this: the computers of end-users tend to be less well administered. Consequently, such computers are more readily invaded, and can come to be under the stealthy control of malicious intruders.
Also, end-users can be less attuned to the evolving rules of etiquette observed on the Internet for server configuration. Sometimes, an end-user intentionally instructs her or his computer to behave in ways which the end-user considers acceptable but which others on the Internet consider abusive.
To prevent end-user computers from being used to send spam directly, either by intruders or by their legitimate users, ISPs tend to block outbound port 25/tcp. TFN does too. This prevents end-users from directly connecting to remote SMTP servers, forcing them to funnel outbound email through the ISP's SMTP servers. This centralizes and facilitates abuse detection and response.
Most ISPs, TFN included, exempt users of static IP addresses from this restriction. Static IP addresses are needed for servers. The thinking is that users who request a static IP address are probably running a server, and are probably better able or at least more willing to fulfil the responsibilities of administering an Internet-connected server. If they do prove abusive, their unchanging IP address makes them easy to trace and to report to the ISP.