Just means that it is a mid-release variation of the initial release version.
Depending on when you download the release version of the server, you will get either no SNAPSHOT or a variation of last uploaded SNAPSHOT.
If you are getting that far, then the server should be running. Whether is stays running when you close out that terminal is dependent on a few things like if/how you are automatically starting it or not, and what the command line you used looks like… did you add the & to the end?
mail.properties is not directly related to your administration account. The mail.properties is for setting up a SMTP process that the server can use to send out AUTH tokens and other data to the various users that sign up to your server.
The admin account is totally different… I have one but set it up a long time ago and rarely use it so I am not completely following what all you might be doing wrong with it. But at a guess, you need to create the admin login and password in the server.properties
