Put this at the end of your ad's

Sorry but we can not be responsible for lost or damaged mail. This
means if the shipper damages or loses the item we send you the
insurance ticket and you deal with the people that damaged or lost the
item. The shippers do not work for us and we can not afford to be
responsible for them breaking or losing your items. We pack with care
and ship fast check out our feedback!

Also require delivery confirmation it's 55 cents, that way they can not
lie and say it was lost in the mail, and the P.O. will have to pay if
insured. Require insurance on everything.

Never pay shipping for refunds NEVER!

Joe