SpinNet

July 31, 2026
SoftBank Corp.

SpinNet's DMARC Policy Update to Enhance Email Security

Dear SpinNet Customers,

Thank you very much for using SpinNet.

To further strengthen email security and protect customers from email spoofing and phishing attacks, SpinNet will update its DMARC (Domain-based Message Authentication, Reporting, and Conformance) policy.

DMARC is an email authentication mechanism that allows domain owners to specify how receiving mail servers should handle messages that fail authentication, such as by quarantining or rejecting them.

This change will help receiving email services identify and block messages that impersonate SpinNet.

Please see below for details.

1. Who is affected

Customers who receive emails from SpinNet email domains
(e.g., @xxx.att.ne.jp)

2. Changes to the DMARC Policy

If the recipient's email service performs DMARC checks, emails that impersonate SpinNet and fail DMARC authentication may be rejected by the receiving email service.

	DMARC Policy (How to Deal with Spoofed Emails)	Effective Date
Current	Quarantine (Receiving email services are requested to place the messages in the spam folder.)	-
New	Reject (Receiving email services are requested to reject the messages.)	Phased rollout beginning September 1, 2026

3. Additional Information

To further protect customers from phishing attacks and other email-based threats, SpinNet is also exploring the introduction of DMARC checks for incoming email.

Further information will be provided once the details have been finalized.

If you have any further questions, please contact the SpinNet Customer Center.