Add support for SMTP Delivery Status Notification (DSN) with the NOTIFY option

[tfranzo]

I would like to propose adding support for SMTP Delivery Status Notifications (DSN) in Thunderbird when sending emails.

Currently, Thunderbird only allows users to request a read receipt (Disposition-Notification-To header), which depends on the recipient's willingness to acknowledge the message. However, Thunderbird does not support SMTP DSN, which allows the receiving mail server to automatically notify the sender of successful delivery, failure, or delays — independently of the recipient’s actions.

The implementation of this feature would enable Thunderbird to send the NOTIFY=SUCCESS,FAILURE,DELAY option in the SMTP MAIL FROM command.

Example:

MAIL FROM:<sender@example.com> NOTIFY=SUCCESS,FAILURE,DELAY

✅ Benefits of this feature:

• Allow professional users to confirm email delivery at the SMTP server level

• Automatically receive a notification if a message fails to deliver or is delayed

• Align Thunderbird’s features with other clients like Outlook that already provide this functionality

Ideally, the feature should:

• Allow users to enable/disable the DSN request per message in the compose window

• Provide a global setting per account to enable DSN by default

Thank you for considering this suggestion, which would enhance Thunderbird's professional capabilities.

[Jon]

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