Dealing with OP25B

Asahi Net has implemented the outbound port 25 blocking, OP25B, to block the outflow of unsolicited bulk emails.

If you happen to experience impacts from OP25B, you may need to review and alter options. Please refer to information below.

Continue Using Non-Asahi Net Email Servers

Use Other Ports beside 25

You can still send emails by using currently using outbound email server of Port 587 (Submission Port) (Japanese), or Port 465 (SMTP over SSL/TLS).

Please check with your email service provider if your outbound mail servers are compatible with these ports.

If you have your own mail servers, please configure to port 587 or port 465 and do not use port 25.

If Port 25 is the Only Available Route (and if you cannot use other ports)

If your mail servers are not compatible with Port 587 (Submission Port) (Japanese), or Port 465 (SMTP over SSL/TLS), please try using Asahi Net email server, or alternatively consider adding Fixed IP options, if you are using FLET’s network.

Use Asahi Net Outbound Mail Server

You can also send emails by using Asahi Net mail server (i.e.: if you have issues sending emails using other providers mail server.

When you configure email software, please make sure that you enter your Asahi Net ID and matching password to process SMTP certification.

Please refer to our configuration guide for major email applications.

  • *Retrieval (POP) server and its matching user name and password must accord with the one registered at your mail address provider.

Add Asahi Net Fixed IP Address Option (IPv4)

NTT FLET’s Network Users

If you use our connection service using NTT FLET’s network, you can enable port 25 by using your own static IP by adding our Fixed IP Address Option.
(Since Asahi Net Fixed IP Address is serviced only in IPv4, connection is not influenced by OP25B)

Please refer to our service page to see details of Fixed IP Address Option

  • *Fixed IP Address Option provides only with IPv4.

Relay Server

It is possible to send emails by placing via Asahi Net designated relay server from your home mail server when you use Asahi Net internet connection service with our dynamic IP address connected line.

  • *We do not provide support for relay server. Thank you for your understanding.


Please refer to FAQs for more details on OP25B

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