[tgsovlerkhgsel]

"our EDDM vendor" seems to imply a third party getting the addresses to print (because there's no need to keep the vendor name secret if it's the USPS), but maybe they just thought it sounds better than saying "the USPS".

[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.