Add LocalEndPoint to EmailConnectionInfo

[jag43]

EmailConnectionInfo could do with having a LocalEndPoint property.

In our case we have a few different apps running on one machine and they all send emails.
To prevent them from fighting over port 25 we are using MailKit's LocalEndPoint property (set to 0 and it will pick up one that is free).

I'm not how this would work with the System.Net.Mail version though as there is no equivalent there.