I am trying to pull Subject Lines from a separate data extension than our sendable data extension. There are different subject lines stored here, and they vary by each record.
I'm using the LookUp() function, but for some reason it only works if I choose the data extension that I am supposed to be looking up for a send preview in Exacttarget.
So let's say my sendable data extension is called "SendableDE" (creative, right?) and the data extension that I am looking up is "DEWithSubjectLines". For example, I have
%%[SET @subjectLine = Lookup("DEWithSubjectLines","SUBJ_LINE","SUB_KEY",_subscriberkey)]%% Returns: %%=v(@subjectLine)=%%
So, if I choose "SendableDE" when I do a Send Preview in ET, the function returns nothing.
But, if I choose "DEWithSubjectLines" when I do a send preview, the dynamic subject line is returned as intended and changes as I click through the different records. But why would it only work with that data extension? That pretty much defeats the purpose of the LookUp function.
I must be missing something conceptually here. Any thoughts? Thanks!
P.S. I also tried this:
%%[SET @subjectLine = Lookup("DEWithSubjectLines","SUBJ_LINE","SUB_KEY",SUB_KEY)]%% Returns: %%=v(@subjectLine)=%%