Are you referring to being notified when recipients receive the message? That service has never been reliable because it is dependent on the recipients. But maybe you are referring to something else.

Hello david,

I am referring to ask for a Delivery Notification status to be delivered back to me,,, I am NOT referring to a receipt request from the recipient(s) !  And Yes  a Delivery Notification has always worked reliably under 'options' when sending  an email.  I'm thinking that's exactly why Mozilla placed that within 'Options' in Thunderbird to begin with, why else would it even be there? As I mentioned it has always worked but  stopped working almost a year ago~!

Fiddlah

If you are referring to RFC 3461, it's not possible to say if your mail server support this feature for outgoing mail, because it may be offered only to customers, so it's not possible for external people to know. Try to connect to your mail server using openssl and look at the output for the EHLO command, if a 'DSN' is returned your mail server supports this extension.

SImilar to return receipts, this is an optional service and an extra load on the networks, so don't expect it to be routine, and it it is NEVER a responsibility of Thunderbird. This service is normally provided only when a message cannot be delivered, and that is done whether requested or not.

Maybe Breezeline or Thunderbird, Ver 103.3.2 deactivated support of Delivery-Status Notifications. Inbox.Lv supports Delivery-Status Notifications: Thunderbird/91.13.1 and Thunderbird/102.6.1 succeed.

Delivery-Status Notifications are important proofs that lying recipients really received e-mails.