Is .NET 3.5 installed?

Take a look at these for diagnosis/related workarounds:

https://support.microsoft.com/en-us/topic/kb3186435-fix-sql-server-2016-database-mail-does-not-work-on-a-computer-that-does-not-have-the-net-framework-3-5-installed-or-stops-working-after-applying-sql-server-update-3480beb6-1329-74d6-0f3a-e8e3d893326c

https://joeydantoni.com/2016/07/27/sql-server-2016-database-mail-not-working/

1. Can you provide DDL (including indexes) for the referenced tables?

2. Eliminate the left join to vwFirstSynonymika -- you aren't even referencing it. And we don't know what lurks in...

dbo always exists. The table "[dbo].[ChannelReading_940860_11_34216228-4C4A-4137-AEA5-EFA9D6A88364_MainLevelData]" does not exist in the database in which you are executing.

To prove it to yourself, just execute

To prove it to yourself,...

Test data (not sure how to display it):

As insert statement(s) -- e.g.,

INSERT INTO #table (Column1, Column2, etc.)
SELECT Column1, Column2, Column3
UNION ALL 
SELECT Column1, Column2, Column3;

-- or

INSERT INTO #table...

dbo.mails is your data table, not a SQL Server Database Mail table.

If you don't want all the recipients returned by your query, then you need to either edit the data...

Do you have a server connection open in Object Explorer when you open the file? Is the server group selected rather than a specific server connection when you open the...

Is this ORM generated code? You have a bunch of parameters using nvarchar(4000), even though none of your columns are nvarchar(4000).

The worst offender that is likely to be causing implicit...

An identity/sequence is fine for a primary key, especially if it's very expensive to define a unique key (i.e., requires many columns, especially if they're big -- e.g., long strings),...

parent_object_id is in sys.objects in the main body of the query. And subqueries inherently reference

You need to always specify the table/alias name for all columns in subqueries. By it's nature,...

Why are you grouping by DonationYear when you're not selecting it? You could get multiple summary rows w/o the context of DonationYear.

What are the business rules/algorithm for ReceiptNumber?  Just an...

Yes, widespread availability of higher internet speeds & the massive growth in open-source software are factors.

Much of it is about flexibility & ease of change -- scaling up, down, &...

Unless you explicitly convert the datetimeoffset to the correct UTC time -- e.g., for SQL 2012 --

SWITCHOFFSET(@ComparisonDateAsDTO,'+00:00')

--  datediff or less than/greater than comparisons effectively ignore/strip off the...

Deleted

Do you really have a space after the comma in the strings? If so, you'll need to trim that.

This will handle the re-split (assuming the strings are consistent... Is the...

In Windows 10/11, I get it when I right click the Start Menu icon, and select properties. Then on the Shortcut tab, click Advanced. "Run as Administrator" checkbox is on...