your message could not,be delivered to one or more recipients.

Peter Lebbing peter at
Thu Nov 16 16:22:30 CET 2017

On 16/11/17 14:55, Jean-David Beyer wrote:
> From where does it get port 451? My SMTP port is 465
> is my ISP for e-mail: AOL.

It's probably not a port. Note that the port 465 you are using to submit
mail has nothing to do with how mail is delivered from there on. Port
465 is never used between mail servers[1].

It's probably SMTP status code 451, which is a temporary error message
inviting the sending server to try again at a later time. Combined with
the error message, I'm inclined to think it's a greylisting system on
the receiving server. But apparently your ISP's mail server has given up
on trying to deliver it and bounced it to you. Either your ISP is giving
up too soon, or the receiving server is holding it off for too long. The
latter might be because of a configuration error.

The mail I'm replying to got through, though.

I have to admit the formatting of the message with the 451 code was
pretty odd, "deliver mail from 451 <jeandavid8 at>" like the
451 is somehow part of the address. Weird.



[1] Unless someone explicitly configures two mail servers to chat to
each other on that port because... well, because they wanted to do that.
A mail server can be configured to inscribe your mail on a stone with a
chisel if you configure it to do so, but that doesn't mean it's a normal
thing to do.

I use the GNU Privacy Guard (GnuPG) in combination with Enigmail.
You can send me encrypted mail if you want some privacy.
My key is available at <>

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