Tools
On the Tools tab located in settings you will find 3 options. These tools are designed primarily to help administrators solve network problems but they can also be used to probe the configuration of other mail systems.

MX Lookup
This will attempt to use the Outgoing Mail settings to download the MX records of a domain. MX records are a bit like sign posts, giving directions to incoming mails to the computer who is designated to receive them. When you send an email from your computer, it is usually sent to a outgoing SMTP (eg. Ability Mail Server) which is then responsible for deciding where to send the email. It makes this decision based on the MX records for that emails domain (the domain is the part after the @ symbol in the email address). The MX records are stored on the domains DNS and come in the form of a table of domains and their priority levels. The entry in the list with the lowest priority value is used first, and upon failure, the next entry is used (in the order of lowest value priority to the highest). All domains need at least one entry to ensure email works, and this should be the host or IP address of the computer running the mail server for that domain.

DNS List
This will attempt to retrieve the DNS list stored on the computer. If you have enabled automatic detection of DNS information in Outgoing Mails then this is the list of hosts which are being used.

What SMTP?
After giving the host or IP address of an SMTP server you want to query, the mail server will connect to port 25 and display the first line of the response received. Usually mail server software sends the name of the software and version number in the first line. This can there fore be used to identify what software a mail system is using.