Hi Folks, I'm hoping someone with the expertise can help me!
In connection with trying to diagnose email delivery problems to a particular domain, I'd like to know the answer to the following.
My email procedure is: 1. Compose the email "off-line" in my MUA (XFMail) 2. "Send" it -- so it goes in the outbox 3. Really send it (batch send) -- XFMail hands the outbox over to sendmail which then does SMTP with the mail server of my ISP (Zen).
Up to this point, there is no problem; and receipt of a "check" Bcc: sent to me on an external email account via the ISP verifies that the ISP accepted the mail for delivery. And of course I usually have no problems with delivery of emails to their destinations by the ISP. Except for this one domain.
Now the question. When my sendamil is doing its SMTP with Zen's mail server, the first substantive request it will make is
mail from: <whatever.my.sendmail.uses>
After the mail has been received by the ISP, the ISP's mail servers will try to initiate connections with the destination domain's mail server. Again, once a connnection is established, the first substantive request it will make will be of the form:
mail from: <whatever.my.ISP.uses>
My question is: What (if any) is the relationship between
<whatever.my.sendmail.uses>
and
<whatever.my.ISP.uses>
??
Does <whatever.my.ISP.uses> take the email address from the "From:" header in the email? From the "envelope-from"? Or does it uses its own version, as in (e.g.):
mailer-daemon@zen.co.uk
Or what?
One aspect of the background to this question is that, when I try myself to do a (test) manual SMTP dialogue with one of the remote domains mail servers, while I may well get through and successfully send the mail, on many other occasions I will get a response to "mail from:" on the lines of
mail from: Ted.Harding@manchester.ac.uk 451 4.3.2 Please try again later
which will be repeated indefinitely if I keep trying. So I'm wondering if it may be a negative response to the email address used in the "mail from:" request, or has some other reason. Since I don't know whether Zen's mail server would use the same (or similar) email address in its own "mail from:" request, I can't (as yet) link the delivery failures I get with my own SMTP dialogue with the delivery failures when Zen tries to forward my emails to the destination domain.
[And, by the way, how should I interpret the error message 451 4.3.2 Please try again later ??]
With thanks, Ted.
-------------------------------------------------------------------- E-Mail: (Ted Harding) ted.harding@nessie.mcc.ac.uk Fax-to-email: +44 (0)870 094 0861 Date: 15-Nov-07 Time: 11:36:23 ------------------------------ XFMail ------------------------------