I maybe have an idea. If this is the problem I'm thinking of, it's not a problem of Magento.
Sometimes, a customer wants a shop, but also already has a homepage for his domain. For sending emails from a domain, when you register a domain, you usually get a mailserver that's responsible for this specific domain. This "being responsible for a domain" can be checked. Open the supertool and use
mx:anydomain.com. This will show you the mailserver that's responsible for this domain.
Now, Magento supports sending mail only through a local MTA (mail transfer agent, basically the program that takes the mail and contacts the servers to pass them along). Now imagine that the customer has in Magento configured his mails to be sent from
email@example.com. Now customerdomain.com already has a mailserver that is responsible for it, which you can check with supertool.
What now happens: The magento servers MTA takes the mail and connects to the mailserver where the mail should go (the domain from the "to:" address). However, there's a mechanism that the destination server can (and most of the time does) use to determine if the server he's talking to (the magento server) is allowed to send mails from that address (
customerdomain.com): The also checks what you check with supertool. Then he compares who he is talking to to who is responsible for the domain of the
from: address. And if these two don't match, we have a problem.
3 things can happen, and I know of instances of all 3 happening:
- The mail gets delivered.
- The mail gets delivered, but sent to the SPAM folder.
- The mail gets rejected or dropped.
If your MTA is good, you might find information about what happened with the mail in your system logs (
/var/log/mail*). If what I described here is the case, you can add a module that supports sending of Magento mails via external mail server.