My ISP proxies SMTP port 25 - is there an alternative port?
Many ISPs now proxy SMTP connections - this can help them reduce the amount of SPAM - however, it also forces you to use their SMTP (outgoing mail) servers with the problems that may introduce.
ISPs usually only proxy the default 'port 25' that is used for SMTP - AuthSMTP runs on other ports to get around that and allows you to continue to send mail through our service. The ports available are 23, 25, 26, 325 (non-SSL only) and 2525.