My prefix bends bridges and branches in dozens.

My suffix sends mail with what one-hundred governs.

My infix appears three times, hectic and scattered.

I meet engineers, for the looks always mattered.

This might be pretty easy... but that won't receive the $100$ rep bounty award.
You would have to find a secret word in this riddle, involving the numbers, if you want that award.
The numbers also include $16$.

_{I would give out $50$ instead, but it was my birthday recently, so I am being kind :)}