SMTP port: 25

Recently, many internet providers provide the hikari fiber service in Japan. Have you ever tried accessing to some mail server different with mail server of the providers?

I still didn't investigate all but in case of Nifty, i couldn't access to external mail server with port 25(SMPT). The issue is Nifty just allows to use port 25 for accessing
to their mail server only. In case we want to access to external mail server, we must use port 587 instead.

Good look and hope you can send/receive your mail without trouble when changing ADSL serivce to Hikari fiber.