I am a first time seller and was wondering if a priority mailing envelope (the tyvek waterproof kind) has to be flat or can it be very lumpy since it not flat rate? This is for a stuffed animal.
Why not buy a plain bubble envelope and ship it first class and not have to care if it's lumpy?
priority envelopes do not have to be flat...but why not ship it in a box? It will cost very little (if any) more.
Of course Tyvek can be lumpy. It's not Flat Rate, so it can be as lumpy as you want.
That type envelope would be fine however as you are shipping 3 together you may want to check into shipping them in either a box or a poly mailer. If they are the standard size dogs it may be a tight fit otherwise.
If the dogs cannot stand to be smashed, put them in a box. Lots of heavy stuff gets thrown on top of packages that are in transit.
When you ship items, make sure they are packed well enough to make the trip.