24 hours in the life of an email server

I was looking at our main email server statistics for the last 24 hours and thought I’d share a few:

The server blocked 55% of all connection attempts immediately before they even got to trying to send, all thanks to a single Real-time Blackhole List (RBL) we check all inbound connections against on our email servers. The RBL in use has never generated any false positives in all the years we’ve been running with this.

Of the rest of the connection attempts, the server then rejected a further 22% for issues such as attempting to send without authenticating, unknown user/mailbox etc.

So only 31% of the connections to the email server in the last 24 hours turned out to be something we could deliver.

Within that 31%, there will also be all the usual spam and other unsolicited messages, so the volume of legitimate emails will actually be a lot lower than even this figure.

I checked for any messages that had a spam score on our spam filter of 3 or higher (usually a good indicator) and the figure for August 1st was 15% (i.e. approx. 15% of the 31% will be spam).

So in other words, as a rough guess, over the last 24 hours, approximately only a quarter / 25% of all connections to the email service resulted in a legitimate message being delivered.

In addition to all of the above, the server also has to handle all the legitimate POP3 and IMAP connections (inbound messages from the server to our customers computers), webmail services and also fend off regular brute force attacks where attackers are trying random email addresses / passwords to try and break into users email accounts to use them for spamming. The attacks in particular use significant server resources and we have to make sure the systems are powerful enough to just ride these out if necessary.

Keep good passwords on your mailboxes! More about passwords can be found in our previous article here:
http://www.ecologicalhosting.com/news/password-security-17-05-2013

I hope this little insight is interesting. Have a great weekend!

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