Is PEE compatible to SMTP?

SMTP stands for Simple Mail Transfer Protocol and is our current and most widespread mail protocol. It is text based and more than 40 years old. This protocol uses (and adds) an abundance of header information to each e-mail that makes it vulnerable to a certain kind of attack (mass surveillance) that PEE intends to prevent. PEE stands for Privacy Enhanced E-Mail and is a new protocol, designed to cope with today's problems.
These protocols are fundamentally different and not compatible to each other. Making PEE compatible would certainly defeat the purpose. It is therefore not possible to send or receive "classic" SMTP mail using PEE and it will never be.