If you are a system administrator you probably manage one or more email servers so things eventually will go wrong and need to be resolved as quickly as possible. It is beneficial to know how to troubleshoot email servers using telnet via a shell so you don’t have to rely on a GUI mail client. Below I describe how to login to an Exim email server using telnet, authenticate via SMTP authentication, and then send test emails. The below examples will be run from a terminal window on Linux however they should be very similar too running the commands from a Command Prompt on Windows 7 or any other operating systems using a terminal window or similar.
I am a huge fan of Gmail which I use to consolidate multiple email addresses in one location so I can easily search, store, and manage tens of thousands of emails dating years back. One of the issues I run into is archiving email messages or managing more than the default screen of 25 email conversations at a time. There are two tricks that can assist you managing more than 25 messages at a time using the Gmail web interface which I explain in more detail below. It is also possible to use an email client such as Microsoft Outlook to drag and drop email messages between folders or labels as they are known within Gmail.
Last night I upgraded the BIOS on my Dell Studio XPS 13 from A11 to A14. The BIOS upgrade appeared to work without issue however when the computer rebooted with the new BIOS version I received a boot error and then once I skipped the error I received a popup message within Windows 7 as well. The problem ended up being something really silly which is explained below but I wanted to note in case someone else ran into the same issue.
This topic is fairly known to most older system administrators however I doubt it is used very often anymore. If you happen to manage any servers where there are typically various people logged in and working on different items from the CLI then it can be useful to be able to send them messages. Using the write command you can send messages to users logged in on specific TTY port or by username. Below are a couple examples of how you would use the write command from a Linux shell.
I installed ISPConfig awhile back on a web hosting server that at one point also hosted email accounts. I recently moved all of the email to a different server and wanted to cut down on CPU and memory usage so I needed to disable amavisd, clamd, courier-imap, and courier-authlib. These services provided a way to receive email via POP3 and IMAP as well as content filtering and virus scanning for all of that email. So after shutting all of the services down I needed to remove the reference to the local content filter from Postfix because if amavis is shut down and mail is sent from a web application to the localhost then the connection will be refused and Postfix will not send the email. Below I describe the Postfix configuration lines to comment out as well as a way to reload all of the queued email into the Postfix queue so it could be sent again.