dusty wrote:
My mailbox is in front of my house and unfortunately lies along a
concave curve, not very sharp, but sharp enough that either the
mailman or a car has hit it three or four times over a couple of decades.

The box itself is bolted to a 4x4, then this goes into a patented flex
adapter that allows the top 2 feet of post and the mailbox to flex if
anyone touches it. The bottom 2 feet or so then feeds into a 4x4
bracket that is bolted to a concrete sidewalk at the four corners of
the bracket with 5/8" lag bolts and lead anchors in the concrete.

Although the lag bolt/ lead anchor system has worked, one or more of
the bolts seems to work out over time making the bracket and therefore
the entire box and post unstable. This week after the box was struck
by the mailman and toppled over, I was thinking of changing out the
lag bolts for something else. I wasn't sure what. I spotted some
"wedge anchors" in the hardware store, specifically for concrete, but
no one there could tell me how they worked. I was also thinking of
using some sort of concrete epoxy to glue stainless steel studs into
the concrete and then just attach the bracket with ss nuts.

Not sure if I should do it or not. The lead anchors seem to "give" if
anyone hits the box, but concreted studs probably won't.

Opinions welcome and thanks in advance.

Use something like this or a wedge anchor. They won't fail.

https://www.homedepot.com/p/Simpson-...-RP2/100375203