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Use following command in SQL Server Management Studio to know your login name:
select suser_sname()
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While I am not 100% sure, it would be any user name in current database as stated in help itself.
This is a security feature. Typically, you should have a separate user for such tasks and that user should be member of this role. This user could be a SQL Server user or a Windows user - if your server is configured for mixed mode authentication.
This way other users (who are obviously are not member of this role) will not be able to send the mail (either deliberately or inadvertently).
Hope you get the point.