Hello OP, Almost all I send is by standard letter rate or large letter rate.

I insure myself by adding a very small percentage to each item for sale to cover the cost of lost items, items not delivered etc.

Most customers are genuine when they tell you they haven't received their item. I ask them to check other members of the household, check with neighbours (around where I live, missing mail is most often miss delivered to a neighbour). I also ask them to check at their local PO to make sure it isn't waiting for them to pick up. It is surprising how many come back a day or two later and tell you they have got it and what happened to it.

If the item still hasn't turned up, I post another. Then I decide whether to block that buyer on the basis of their attitude when making contact.

A couple of customers have become regulars, so don't jump to conclusions too quickly.

I have found overall, Australia Post is very reliable, just a very very small number of items go missing and most of those do turn up. In fact I would have to say the most unreliable service by AP is in fact Express Post. LOL