How to automatically allow Letter format printing on A4

Device: E525w

I am located in Europe, so I only have A4 in the printer. I do have a number of documents originating from US colleagues on Letter format. I am not able to change those.

When I print those documents the pringer starts bleeping, and I have to hit the OK button to continue printing on A4 paper.

How to I arrange that the printer automatically continues regardless if the papersize is Letter or A4?