Certain email addresses do not meet the specifications and requirements defined by the RFC (Request for Comments).
Most non-RFC compliant email addresses are mobile phone email addresses (carrier emails such as @docomo.ne.jp, @ezweb.ne.jp, and @i.softbank.jp).
While these non-RFC-compliant email addresses may be able to send and receive between mobile phones of the same carrier, they may not be able to send or receive mail from other carriers.
Since April 2009, mobile phone carriers have issued RFC-compliant email addresses only.
[Examples of non-RFC compliant email addresses]
1. A period (.) directly before the at-mark (@) or at the beginning of the email address.
Example 1: .abcd@example.co.jp
Example 2: abcd.@example.co.jp
2. Multiple consecutive periods (.) before the at-mark (@).
Example 1: abcd..@example.co.jp
Example 2: ab..cd@example.co.jp
3. The address contains characters other than half-width alphanumeric characters and a limited set of symbols (. ! # $ % & ‘ * + ? / = ? ^ _ ' { | } ~).
Example 1: ab[cd@example.co.jp
Example 2: ab@cd@example.co.jp
If you have a non-RFC-compliant email address registered, you may not receive important emails, such as notifications of suspicious login activity or password changes.
You may also experience authentication errors during payment procedures, which can prevent transactions from being completed.
We strongly suggest updating to a different email address via [Change Email Address].
We highly recommend making this change, as we often see cases where users do not receive emails from us.