SQL: Database Mail - Not sending

Issue:
msdb.dbo.sp_send_dbmail is not sending mail but executing successfully

Other Symptoms:

When SP with the sp_send_dbmai stored procedure, it shows that the SP has executed successfully but displays that the Mail is queued

Other Checking:
1. Management > Database Mail > View Database Mail Log
- There are no instances that the Database Mail process has started

Resolution:
1. Send a Test Email via Management > Database Mail

.. Afterwads, everything worked okay, weird but it worked for me :)