cPanel's Email Routing module offers the user four options. It's not really clear when each choice is approriate. This article will explain.
In most cases, Automatically Detect Configuration is the right choice. cPanel takes a look at the MX (Mail eXchanger) records in the local DNS, and if that record indicates a different mail server, it selects remote. Otherwise it selects local.
The exceptions occur when your setup isn't what cPanel assumes. If the domain's name servers aren't referencing your DNS server, then cPanel will usually make the wrong choice. There's a few common cases when this happens:
- Your customer manages their own DNS
- You're building a new site and the existing site is on another server that's handling DNS
In both of these cases, you want to manually select Remote Mail Exchanger. cPanel creates a DNS entry for every domain it manages, and it assumes that the name servers reference that DNS entry. When it checks the MX records, it doesn't go to the "real" DNS for that domain, so it won't get the right information.
When a customer is using their own DNS their mail won't be affected if the setting is wrong, but any mail set from the local server will be handled by cPanel. As a result the messages may be rejected, discarded, or end up in the default email account.
What about Backup Mail Exchanger? This is a relatively rare occurrence. It's unlikely to happen when the local DNS is being used. This would come up when a domain has multiple MX records, and one of the secondary records references our server. It tells cPanel that mail might be received in the event that all mail servers with a higher priority fail to respond.
Signs that Your Setup is WrongIf mail from your server isn't being delivered, then a common cause is an incorrect Mail Routing setting. Take a look at the Track Delivery module under Email to confirm that this is the cause.
You can also check the system / default mail account for clues. Go into Email Accounts, select the default mail account tab, and then "Access webmail" to see if there's anything relevant there.