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 :) Note: This is genuinely true and not part of the riddle.}

Hint:

$100=10\times 10$... but that is not necessarily true for Romans.