If you check the "My server requires authentication" checkbox and click the "Settings" button next to it the below dialog box will appear.
These settings are for your outgoing mail server. If you are using the same server to send and receive your mail, you leave this selected to "Use same settings as my incoming mail server". If you are using a different server to send mail than you use to receive mail, you can select the "Log on using" radio button, then fill in you account name and password.
These extra settings may be necessary because of how email is configured to prevent unauthorized SPAM. Tto prevent people from using mail servers (to send SPAM) without permission it is necessary to require authentication to send mail. Many Internet Service Providers (ISPs) also require that users are dialed into their network to send mail even with the authentication. This means that you will not likely be able to send mail through an ISPs mail server unless you use their account to connect to the internet. For example, if you have an Earthlink ISP and an AT&T ISP, Earthlink will not allow you to send mail through their mail server even if you have the proper authentication as long as you are using an AT&T account to connect to the internet. Therefore depending on your organization's mail policy, you may need to use your ISP account to send your mail even if you are receiving your email on a different work account.