What is DSN in email?
Delivery Status Notification (DSN) has been around sinceRFC 821(1982).
This old convention either meant that you received an warning pop-up or you received nothing.
The email may have arrived or it may not have arrived.
The error messages, in many cases, were just as helpful as no error messages.
It is a set of extensions to the MAIL and RCPT commands.
If it responds with DSN somewhere in the feature list, it will be able to serve requests.
If not, try another server or fall back to email without DSN.
With DSN, this is no different.
But there are two additional options you may issue: RET and ENVID.
Valid arguments are FULL and HDRS.
FULL means that the complete message should be included in the error alert.
HDRS instructs the server to only return the headers of the failed mail.
If RET is not specified, it is up to the server what to do.
In most cases, HDRS is the default value.
Its purpose is to tell the sender which email a possibly issued warning pop-up corresponds to.
The format of this ID is left to the imagination of the sender.
NOTIFY is the core of DSN.
It tells the server when to send a delivery status notification.
The options include:
NEVER must be the only argument if it specified.
The other three may appear in a list, delimited by a comma.
The argument for this option is the email address of the original recipient together with the address key in.
The address key in comes first, followed by a semicolon, and, finally, the address.
Recipient ok (will queue)
This is followed by the DATA and a delivery status notification of success.
Does DSN Work?
DSN only works if the mail transport agents from sender to recipient support DSN.
