Pinal Dave’s blog has been one of my go-to blogs as a SQL DBA for a long time.
I remembered a similar situation in one of our servers when he blogged about a DB mail issue with the error message.
In our scenario, a SQL Server task using the SSIS Package to send emails to the development team was failing with the error below.
The SMTP Server Requires a Secure Connection or the Client Was Not Authenticated. The Server Response Was: 5.5.1
Only one of the server’s jobs that used Database mail was experiencing this difficulty. While successful tasks had part of the connection string as ‘EnableSSL= True,’ further investigation of the package revealed that unsuccessful jobs had part of the connection string as ‘EnableSSL= False.’
The connection string for the job that was failing was set to ‘EnableSSL = False’.
The job was corrected when the connection string was fixed, and it was running successfully.
For more fixes related to this error message see Pinal’s blog posts