There are some cases, where a failed drive in our RAID array can cause serious issues. For example, due to the failed drive, our Linux system can shutdown and it won't be able to boot again. The GRUB bootloader might also fail and will need to be reinstalled. We have few options, one of which is to reassemble our RAID array from any other Linux LiveCD distribution. Of course, first we need to physically replace the failed drive and then boot to our LiveCD. Once we have booted, we need to install the mdadm tool.
You might be asking yourself why you might need such configuration. Well, some Internet Service Providers or hosting companies block the default SMTP port 25. If that is the case and port 25 cannot be unblocked, we can use alternative solutions. Such solution is relaying email via other port such as 587. Google's Gmail offers such capabilities and you can use your own Gmail account in order to send messages from your server. Here is how you can do it with few simple steps: