These days many personal email accounts are hosted on cloud servers, leaving many web servers without the need to send and deliver emails to their users. For plenty of businesses, however, having a mail server is still very much a part of the dedicated server experience.
If you host your own mail server, whether Postfix, Sendmail, or something else, you need to make sure it is reliable and secure. Under normal conditions, a mail server does not place a heavy burden on a dedicated server, even with spam filtering and virus scanning. In some instances, however, something goes wrong, causing the mail server to use more than its fair share of CPU cycles and RAM. To investigate, consider the following:
1. Are your server logs showing a dramatic increase in mail server activity? It may be that you truly are just seeing in influx in the amount of mail sent on a particular day, but it could also be an attack on your server.
2. Check your mail server’s security and make sure someone has not hijacked it to send spam. This is a very common thing for spammers to do, exploiting a user’s account or an open relay on the SMTP server to send spam to people all over the world.
3. It could be that your server is receiving a spam attack, where it receives a large amount of spam, significantly more than usual. This could be intentional or just be a bad day for email.
Once you locate the source of the problem, you can start looking for solutions. Some problems will go away with time while others require action.