With conversation threading (which almost everyone has enabled), Gmail was trimming the bottom of the emails we send with our new app because they were too similar to the other emails in the conversation thread.
They’re similar because that’s just the link to get back into the app—you know, the important bit to keep our users engaged! Having that trimmed is bad.
The solution to this is silly: Gmail will not trim content if it’s always unique, so now we add a unique/random number to the bottom of every email we send. Insert eye roll.