Oct
13th

Server Tuneup – Email

Filed under Server Tips | Posted by Gary

This is the first in a series of tips that will delve into CPanel and soem of the options you have. The first one I’m going to look at is the ‘default email address’.

If you look in the email section of CPanel you’ll see this option. Depending on which version of CPanel is installed, you may see it as a ‘Default Address’ icon or you may need to first click on ‘Email Accounts’ to see it.

You should have 3 or options (you might need to click on ‘Advanced’ to see the third option) but we will look at the main three. In CPanel 11 you can ‘pipe’ messages but that is for advanced users and rarely used.

First, lets talk about what this ‘default address’ is. The default address is a ‘catch all’ address that will receive email for any email address that isn’t actually defined. So, you may have a few addresses like bob@… and sally@… but what happens if an email comes in for fred@…? That’s where the default address comes in. The email to fred@… will be delivered to the ‘default address’.

There are a few reasons why you may want these messages delivered into a mailbox, but generally speaking you will want to discard them. This is mainly because many spammers will send emails to non-existent addresses at your domain in the hope that they are delivering to a real person. This is called a dictionary attack where they take a list of several thousand names and send email to all of those names at your domain.

Bouncing the messages is considered to be the technically correct thing to do though there are some who frown on this as it simply creates more email out on the Internet and if the incorrectly addressed emails are coming from spammers then they aren’t going to even read the bounce messages anyway. Also, there will probably be a time when a spammer forges an address at your domain as the reply address on spam emails in which case your server will receive many bounce messages as well … which it will then respond to with more bounce messages.

Fortunately, CPanel allows you to deal with these message without creating more messages. The option (in CPanel 11) is ‘Discard with error to sender (at SMTP time)’. This looks at the address that someone is trying to send to and if the address does not exist it simply responds with an error message ‘no such user here’ and closes the connection. It’s basically like when you ring a wrong number on the telephone. The person at the other end picks up, tells you that the person you are calling is not at that number and the call ends.

The one exception to this option is if you are experiencing a sustained, heavy flow of emails to invalid addresses. In this case you may want to select the option that says ‘Discard (Not Recommended)’. In earlier versions of CPanel this is the ‘:blackhole:’ option. Discarding with no error response will lower the amount of CPU and resources required for each invalid messages and may prevent your server from slowing right down or even crashing. If this does happen and is sustained for more than an hour or two then you really should contact your host or a server professional to take further steps in preventing these email messages from getting to your server.

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