Message size limits and notification messages

Administrative limits on message size can have interactions with notification messages.

First, note that it is very important to ensure that users can receive notification messages when messages they send can not be delivered. And note that bounce messages (non-delivery notifications) will sometimes  include the contents of the originally sent message; so a non-delivery  notification may be larger than the originally sent message. So when imposing administrative limits on message size, it is wise practice to  make the limit on the size of message that may be received somewhat  larger than the limit on the size of message that may be sent.

New behavior in MS 6.3-0.15 is that during address reversal of the  envelope return address (envelope From address) of a message, the MTA  fetches the block limit associated with that envelope return address  and will set the NOTARY (RFCs 1891-1894) flag RET=HDRS (return only  message header lines, not message content) on the message if no  explicit return policy was already specified and the message size  exceeds the block limit. This reduces cases where non-delivery reports regarding large messages are undeliverable themselves due to size.

The MTA options    and ,  channel options such as   , and user LDAP  attributes such as    (or more precisely, whatever attribute is named by the   MTA option),  can all affect what  (whether and how much of an original message) gets included in  notification messages.

See also:
 * Address reversal
 * bounce_block_limit MTA Option
 * content_return_block_limit MTA Option
 * ldap_blocklimit MTA Option
 * blocklimit Option
 * Notification messages