Re: Some POP3 mail undeliverable
- From: Joe <joe@xxxxxxxxxxxxxx>
- Date: Sat, 04 Jul 2009 21:16:15 +0100
AlanR wrote:
Hi,
I am having a problem where POP3 mail is not always delivered to the client's mailbox but turns up in the mailbox designated for undeliverable pop3 mail. When this happens the header information is missing. Is there anyway to recover it because I need to see why it is undeliverable.
It seems very unlikely that header information is being lost, as this is almost the ultimate sin in handling email. By far the most likely suspects are mailing list and BCC mail, which do not have valid To: headers, not because they are being removed but because they were never there to start with. Pure POP3 cannot deal with these kinds of mail in a domain-wide mailbox.
The mail system is set up with a global mailbox and mail is then distributed using Routing rules. The ISP has an email domain of the form mydomain.ISP.co.uk. I have my own domain of the form mydomain.com and mail is routed from my domain provider to my ISP and then to the global mailbox. I suspect that the problem may have something to do with the routing rules bur I seem to have every possible variation covered. Any advise would be gratefully received, thanks
Email routing by SMTP does not depend on headers, but on the recipient name used in the SMTP transaction. This is not part of the headers, and may not survive being placed in a POP3 mailbox. It can only survive if one of the SMTP servers which handles the email explicitly adds a header called 'Envelope-To:' or something similar. Many POP3 downloaders can make use of this kind of header, the SBS2003 one cannot.
If for some reason there is no To: or CC: header, such as with BCC or a mailing list (which is just a big BCC mailing), the SBS2003 POP3 downloader does not know where to deliver the mail. Almost certainly, this is the problem. The correct answer is to use SMTP for mail collection. If there is some seriously immovable objection to doing this, and there are few valid ones, there are broadly two options:
1. Use a third-party POP3 downloader, after checking that a) your ISP is adding or checking for an Envelope-To: or similar header, and b) that the downloader can make use of it for routing.
2. If the ISP allows it, do not use a domain-wide POP3 mailbox, switch to individual mailboxes for each user with a few for 'sales' and so on. The SMTP envelope information will be used at the POP3 server to drop the mail into the right mailbox, with a domain-wide mailbox it all gets thrown in together. When the boss tells you that he must have a catch-all mailbox to avoid losing sales due to typos, tell him that the SMTP system very quickly tells a sender when the recipient is non-existent, and it is better to do this than to allow the sender to continue to use an incorrect email address and maybe pass it on to others as well.
But SMTP all the way to Exchange is better.
--
Joe
.
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