@facujb
No seller would send an item before being paid.
Even if it was on hold that would be between the seller and paypal as the seller may be subject to the 'new seller hold' but that does not affect your buyer protection at all.
What buyer protection you have depends on many factors all listed in Paypals buyer protection policy for you to read so you can risk assess your transactions.
Legal (bottom right of Paypals pages) > user agreement > buyer protection.
Advice is voluntary.
Kudos / Solution appreciated.
