RFC3463 Enhanced Mail System Status Codes defines in 3.6 Mail Delivery Protocol
X.5.3 Too many recipients
More recipients were specified for the message than could have
been delivered by the protocol. This error should normally
result in the segmentation of the message into two, the
remainder of the recipients to be delivered on a subsequent
delivery attempt. It is included in this list in the event
that such segmentation is not possible.
RFC5321 Simple Mail Transfer Protocol says:
4.2.3. Reply Codes in Numeric Order
452 Requested action not taken: insufficient system storage
18.104.22.168.8. Recipients Buffer
The minimum total number of recipients that MUST be buffered is 100
recipients. Rejection of messages (for excessive recipients) with
fewer than 100 RCPT commands is a violation of this specification.
The general principle that relaying SMTP server MUST NOT, and
delivery SMTP servers SHOULD NOT, perform validation tests on message
header fields suggests that messages SHOULD NOT be rejected based on
the total number of recipients shown in header fields. A server that
imposes a limit on the number of recipients MUST behave in an orderly
fashion, such as rejecting additional addresses over its limit rather
than silently discarding addresses previously accepted. A client
that needs to deliver a message containing over 100 RCPT commands
SHOULD be prepared to transmit in 100-recipient "chunks" if the
server declines to accept more than 100 recipients in a single
22.214.171.124.9. Treatment When Limits Exceeded
452 Too many recipients (see below)
4.5.4. Retry Strategies
126.96.36.199. Sending Strategy
contains: … the retry interval SHOULD be at least 30 minutes…
and says nothing about 452 or 4.5.3
Is the number 100 randomly choosen? Obviously, a site can accept 120 RCPTs per
iteration, and for the 121st RCPT reply
with “452 4.5.3 Retry immediately after DATA”.
Are clients supposed to retry immediately after receiving 452 4.5.3?
What is the difference between „452” and „451 4.5.3”?
says 4.5.3 can be combined
only with 451.
Does „452 Requested action not taken: insufficient system storage” mean in 30
minutes there might be more storage, as
opposed to 4.5.3?
What will happen, if a site has one (1) as a minimum total number of recipients
that are buffered?
What is the sending strategy after the total number of recipient per MAIL
FROM:<..>... DATA . is exceeded?
How are 452 and 451 4.5.3 supposed to be different than the retry=0 hint?
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