Wow, that's some pretty ordinary advice. Why would I remove Australia Post as a delivery option? It's there for anybody who wants to use a PO Box,  Parcel Locker or Parcel Collect address. Why do you suggest I should exclude these buyers from purchasing from me? That really doesn't make any sense at all.

Just to further clarify, the problem I was facing was that the buyer selected and paid for Sendle, but refused to provide a delivery address.

Personally, I couldn't give a hoot who delivers their parcel. They're paying for the service, and the carrier is entirely their choice. They could get it delivered by a 6 foot tall bald hermaphrodite riding a three legged camel for all I care, as long as they pay for it. The point is... if they wanted to use a PO Box address, then they could/should have selected Australia Post delivery, and paid for the service - as stipulated in the listing.

Selecting and paying for the cheapest shipping option which is unsuitable for them, and then expecting a free upgrade to a more costly option is just downright rude... and it's not going to happen. If they want the dearer option, they can pay for it - simples.

Since the buyer ignored all messages (both email and SMS) and caused the sale to exceed my advertised handling time, I decided it just wasn't worth the hassle and cancelled the transaction as previously advised.