16.5.4 Handling 4.2.1 Mailbox Busy Error in Response to LMTP Message Data

If the LMTP channel option MAILBOX_BUSY_FAST_RETRY is set to 1 (the default) a 4.2.1 Mailbox busy error in response to LMTP message data is handled by retrying the message after a random but short interval; normal message backoff values do not apply. Setting the option to 0 disables this behavior.