Email port 25 – This is the standard outgoing email port. 99% of the time it will be fine and set in your email program by default.
Email port 26 – This is simply a alternative to port 25 and works the same. It exists because some ISP’s do not allow outgoing email which we believe unless advertised bluntly is bad business conduct. So we have set up a second port for people to get around their misleading ISP’s.
Email port 587 – Is yet another attempt to block email from users. Like most spam blocking attempts blocking all ports for email other then port 587 really does nothing other then create confusion for regular users of the internet. But if you need port 587 then DWHS can open this by request.