In adelphia.powerlink.windows - article
<***@4ax.com>, on Wed, 05 Oct 2005
23:34:51 -0400, Kenneth Grimm says...
Post by Kenneth GrimmWhat does "421 message rejected" mean? And why would someone who is
trying to send me a message be getting it?
Ken
Ken K4XL
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The error message you quoted is likely generated by the sender's
system. The complete error message the sender received should
contain more information
This is a response I found on Adelphia's use of that error message :
----- begin quote -----
Error 421 is a rejection message to a specific email. It is delivered
in a few specific cases.
1. The contacting MTA has sent to many messages in limited time.
2. The contacting MTA has sent to many messages to nonexistent
addresses
3. The message is spam.
The 421 is provided so they can look at their system. Where there is
no forwarding server masking the origin, it would go to the source;
however, by putting themselves in the middle of this process they get
the error.
If the originating provider were to receive the error, they can send
the messages as attachments to ***@adelphia.net; however the
forwarding providers prevent that. We are not removing the 421 and
discarding locally to facilitate forwarding companies.
----- end quote -----
That being said, I believe a 5xx message is called for in a
'rejection', 4xx messages are for 'temporary' errors and should
contain some verbiage. They're effectively telling the sender's mail
server to try again later which can cause problems for some email
servers (the crux of the quoted response above).
The response above implies Adelphia is utilizing it as a
"Challenge/Response" system invoked under certain circumstances. As
such, they should be using a x70 code with diagnostic text pointing
the user to a web page indicating what to do or what the problem is.
What remains to be seen is whether they provide enough information to
the original sender indicating that they need to do something or just
what that something is.
I'd be curious to see the complete error message your acquaintance
received and whether Adelphia is providing adequate diagnostic
verbiage with the error code.