TreatAsContentArea Breaks links when sent to large list

Question

Basically I created an email and part of the content is build by an external system. My content block AMPscript looks like this:

%%[
SET @ID = GUID()
SET @Content = '5JbXByZXNzaW9uUmVnaW9uKCIyMDU3MzAMl8wODEwMTYiKT0lJSA8ZGl2IGRhdGE'
]%%
%%=v(TreatAsContentArea(@ID,Base64Decode(@Content),"WrappingImpressionRegion"))=%%

This works great for small test sends, and the tracking works well on all my seed lists. The problem is when I sent do a large 100k+ list the link tracking within the TACA call stops working entirely. I got 0 clicks accross the board.

Is there a limit to a TACA call or something I could be missing?

I also want to comment that there are multiple TACA calls that look identical to this in the email. They each have a unique ID that is determined by the GUID. Also within the @Content there is an impression region with a unique name.

Any help appreciate!

Answer 1

I figured out the issue. The @ID variable was being uniquely set for each subscriber. This is the offending AMPscript:

SET @ID = GUID()

This causes a problem because the the TACA call has a caching limit and since the @id is unique per subscriber we hit that caching limit and then the TACA call starts failing.

We need to hardcode the @ID like this:

SET @ID = "1234567890"

Answer 2

I have solved this issue in a more generic way, using MD5 checksum of the content as an identifier, i.e.

%%[
SET @Content = "Hello <a href='http://www.salesforce.com'>world</a>"
SET @textChecksum = MD5(@Content)
Output(TreatAsContentArea(@textChecksum,@Content))
]%%

Hence if this same code is reused across one email, you will automatically set unique IDs, but these will still not be set individually for each subscriber. This is especially useful if TreatAsContentArea is used in a content block, and @content is set outside of it.