Customers being charged for extra postage

[Mayvaria]

I’m new to selling on Etsy so maybe I’m just doing everything wrong or It’s not a big issue. At this point I’ve shipped over 200 packages (Free Shipping) with most of them having the same postage. Nearly all of them have arrived without any issues. However I’ve had trouble with a few people who say they are charged for extra postage. I’ve measured and weighed the packages and they’re definitely not over 1 ounce nor are they too thick. Sometimes the extra postage charged is 51 cents and other times it’s 4.51 dollars for the same item. The only thing I can think of that could cause a problem is that it’s too rigid, but I personally don’t see how it could possibly be too rigid. Again this has technically only happened a few times out of over 200 packages, so I’m not sure what to do. Most of the time it’s not an issue so I don’t see a reason to pay more postage especially because I don’t even know how much postage would be enough to ensure this doesn’t happen. But I also don’t want customers paying extra for postage. So I’m kinda just not sure what to do.

[BagmakerSupply]

@Mayvaria: "... a few people who say they are charged for extra postage ..." Are you putting stamps on the package or are you using a third party provider like Etsy labels, PirateShip, Stamps.com, etc? If the latter, you should be charged any adjustments, not the recipient. And you'd be paying less for postage.

[bradgoodell]

Accurate and concise.  

[Mayvaria]

I’ve been doing the Pitney Bowes labels through Etsy. I thought any extra charge would be able to be charged directly to me but that hasn’t happened. The package is just a bubble mailer with a set of earrings typically.

[NanaLetha]

Rigid mailers are considered packages by the post office