Hi, thanks for reaching out!
Waterfalls rely on conditional statements that ensure a column only runs if the previous column meets specific conditions. Deleting columns after the waterfall is created can be problematic, as the results (or absence of results) from these columns are often essential for the rest of the process.
For this reason, we always recommend modifying the waterfall before it is run—by adding or removing data providers, and selecting the email validator, prior to execution.
In short, it's best to adjust the waterfall setup before running it to avoid issues.
Let me know if this clarifies things.
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