[Amezarak]

Someone has to print the mailers. The USPS lists the EDDM vendors on its website and they work through the USPS.

https://printerdirectory.usps.com/listing/#/results

[tgsovlerkhgsel]

The mailer itself and the address can be printed separately. I didn't dive deep enough to confirm it, but I think these companies print the mailer and USPS prints the addresses.