Monitor System Services with Webmin

A dedicated server typically runs several background services or daemons. These may include but are not limited to your web server, database server, and mail server. All of these services need to be running 24/7 to keep them available for your users. When one of the services goes down, you need to know. Webmin has […]

Configure Apt-Get to Send Update Email Notifications

Last week we looked a YUM’s update settings and found a way to make it send email notifications when updates are available. You can accomplish the same setup with APT for Debian-based Linux distributions. The benefit of doing this is to have apt-get do nothing but notify you when updates are available, rather […]

YUM Auto Update Alert

On a dedicated server running CentOS, there are two common options for running system updates: manual or automatic. There are, however, less common options, such as scheduling your own auto updates with a cron job or having your system alert you whenever new updates are available.
There are a couple of reasons why you might […]

Local vs. Cloud Email Services

Traditionally, when an individual or company had their own server, it only made sense to also have their own email system. While web-based services existed, they usually required you to have an email address with rather than
Nowadays, many cloud email service providers offer domain-name capabilities, so that your emails appear to be […]

The Value of SPF Records

SPF stands for Sender Policy Framework, and it is the standard established in RFC 4408. Essentially, SPF validates emails sent to a mail server to determine if a message is spam. One of the biggest problems faced by ISPs trying to fight spam is the spoofing of IP addresses and domains. In […]

How to Fix an Open Relay

According to, an open relay is “a mail server that does not verify that it is authorised to send mail from the email address that a user is trying to send from. Therefore, users would be able to send email originating from any third-party email address they want.”
Using an open relay, someone could […]

Mail Server Email Aliases

An email alias is a name that appears before the @ symbol in an email address, which actually refers to another account or location. For example, the alias “billing” may actually point to an email account on your server called “sales”. A single email account can have multiple aliases, and an alias can […]

How to Change the Port Number in Postfix

The default network SMTP port for Postfix, Sendmail and most other mail servers is 25. This is the port used to send email, and most email clients will use it by default. Unfortunately, some Internet service providers have started to block port 25 because of the high volume of spam sent through it. […]