[Scheduled] 2026/8/26 PORTERS HAISHIN 1.3.0 Release Notes – Help Center

*This page was machine-translated from Japanese and may contain inaccuracies.

We will perform maintenance in connection with the release of PORTERS HAISHIN.
Details of the maintenance and the changes are as follows.

■ Release Work Schedule

2026/8/26 (Wed)　12:00 – 12:30　Japan Time

*Times are shown in 24-hour format.
*The maintenance work hours are subject to change.

■ Impact During Work Time

The service will remain available during the above time period.

■ Feature Additions

A new Bounce Email Management screen has been added.

*This image shows the screen in Japanese.

You can check, on this screen, email addresses that have resulted in a hard bounce (*), as well as email addresses that were excluded from delivery due to a past bounce.
*A hard bounce means that a permanent error, such as a non-existent email address, was detected. Addresses in this state will be excluded from subsequent deliveries.
For an email address shown on the Bounce Email Management screen, if you have, for example, resolved the cause of the error and confirmed that email can now be delivered to it, you can release the address using the [Release] button.
Released email addresses are removed from the list on the Bounce Email Management screen.

*This image shows the screen in Japanese.
Up to 100 records are shown per page; if there are more, they are shown across additional pages.
You can search by email address (partial match).

*This image shows the screen in Japanese.
The resource/ID shown in the "Resource/ID" column is a link, and clicking it takes you to the corresponding list in PORTERS.
The ID refers to the record that was the delivery target in HAISHIN, and shows the information from when the address first resulted in a hard bounce.

*This image shows the screen in Japanese.

The definitions of bounce and drop are described below.
Text shown with a light green background appears in the "Error Details" field on the screen.

*Definitions of Bounce (Hard/Soft) and Drop

Bounce

This is a status, defined by RFC 3463, indicating that the receiving mail server "could not receive" or "did not receive" the email. In other words, this is a case where the email is rejected by the recipient's server after being sent.

Reference: RFC 3463 - Enhanced Mail System Status Codes(Official IETF site)

Hard Bounce
A permanent failure, such as a non-existent recipient address (corresponds to RFC 3463 category "5.x.x (Permanent Failure)").
Email addresses that result in a hard bounce will be excluded before sending in subsequent deliveries.
Soft Bounce
A temporary failure, such as a full mailbox or a temporary server issue (corresponds to RFC 3463 category "4.x.x (Temporary Failure)").
If a soft bounce occurs, a retry (resend) will be attempted.

Drop

This is a case, as defined by the mail delivery system used by HAISHIN, where sending is called off before an attempt is even made.
If a drop occurs, a retry (resend) will be attempted. (However, addresses that have previously bounced and are on the suppression list will not be retried.)

■ Hard Bounce — Permanent Failure (5.x.x)

Code	Meaning	Details / Example
5.1.1	Recipient mailbox does not exist	The email address itself does not exist (e.g., a typo, or an address within a non-existent domain)
5.1.2	Domain does not exist	The domain to the right of the "@" symbol does not exist
5.1.3	Invalid email address format	The address is not a valid email format — for example, a missing "@" symbol, multiple "@" symbols, or no dot in the domain portion
5.2.1	Mailbox is invalid (disabled or deleted)	The address existed in the past but has since been disabled, suspended, or deleted, etc.
5.4.1	Undeliverable routing (No Answer)	The destination domain's MX record is invalid or missing, the destination server is permanently down, the network route itself is broken, etc.
5.5.0	Unclassified protocol status error (Other or undefined protocol status)	A rejection reason specific to the receiving server, an error response from a non-standard implementation, cases with no detailed reason given, etc.
5.7.1	Delivery refused (spam filter, policy violation, etc.)	The recipient address exists, but the message was rejected by the receiving server's spam filter, policy, etc.

*If an unexpected error other than those above occurs, an error description in English may be shown in the "Error Details" field on the screen.

■ Soft Bounce — Temporary Failure (4.x.x)

Code	Meaning
4.2.1	Mailbox disabled and temporarily unable to receive mail (Mailbox disabled, not accepting messages)
4.2.2	Mailbox is full (mailbox full)
4.3.1	Insufficient free space on the server
4.3.2	The system is currently not accepting email (e.g., due to maintenance)
4.4.1	Failed to establish a connection (e.g., timeout)
4.4.2	The connection was disconnected partway through
4.7.1	Temporary policy rejection (e.g., rate limiting, or a temporary block due to reputation)

■ List of Drop Reasons

Reason string	Meaning
Invalid SMTPAPI header	The SMTPAPI header format is invalid
Spam Content	When the spam checker feature is enabled, the content was judged to be spam
Unsubscribed Address	Sent to an address that has unsubscribed
Bounced Address	Excluded because there is a history of failed delivery attempts from this system. *
Spam Reporting Address	Sent to an address that has previously reported the sender as spam
Invalid	The email address itself is invalid
Recipient List over Package Quota	The sending limit for the contracted plan has been exceeded

*"Excluded because there is a history of failed delivery attempts from this system" means the address was excluded because it has a history of bouncing when sent from this same system in the past, including sends made by other companies.

■ Version Information

PORTERS HAISHIN 1.3.0