Problem sending email with SQL Mail

Recently, I encountered a problem sending email
by using SQL Mail system. It was running great under sa login,
but with another login/user I got the following error:

Could not obtain information about Windows NT group/user 'MyUser' error code 0xffff0002.
The problem was found and it occurred due having multiple
Mail/Account Profiles
with no default profile set, meaning one of the profiles must be set as default.

You can set the default by going to:
Management ->Database Mail->Configure Database Mail
and Manage profile security.

Another possible issue, to send Database Mail the user must
be a member of the DatabaseMailUserRole.

You can execute this, to see all members of this group:

EXEC msdb.sys.sp_helprolemember 'DatabaseMailUserRole';