On Tue, 4 Nov 2003 15:45:24 +0200
"Willie Viljoen" <will@???> wrote:
> Follow up:
>
> I decided to also try sending mail to verizon with your address,
> iforbes@???. And received the same error as you encountered, after
> an extremely long time delay. This bothered me, so I tried sending a
> mail from a non-existant domain, and immediately received a 550 error
> telling me I am not allowed to send mail. Error 550 is usually sent to
> deny relaying after an RCPT TO: command for an address the server does
> not own or relay for. Sending 550 after MAIL FROM: is unusual, but
> verizon probably feel it is necisary.
>
> This leeds me to believe that these servers perform a practice known as
> sender verification. Though not uncommon, it is combersome and creates
> long wait times and alot of DNS traffic overhead. Basically, once you
> send the MAIL FROM: command, the server first performs a DNS lookup on
> your domain, once it has found the domain to exist and have a valid MX
> record, it connects to the MX listed and attempts to send a mail back to
> the sender, disconnecting just after RCPT TO: was accepted.
>
> This helps to prevent spam, but causes several problems. I have a hunch
> there is probably some issue with DNS or your primary MX, or perhaps a
> connectivity issue between you and verizon which does not allow the
> verizon server to connect back to yours. This could occur if a major
> overseas line is down and asymetric routing is being used to compensate.
>
> I don't know what else it can be. Check your DNS and mail servers, and
> phone your ISP and make sure their network is functioning properly.
>
> Will
In addition make sure that postmaster can receive mail from a null sender
"<>".
Jerry
--
Jerry Jorgenson
jerry@???
http://www.j3iss.com/
