Loading Envelopes

[NOYB68]

I have OKI 332DN. I print a lot of envelopes. I use the multipurpose tray. I load and print them, but the printer 'always' asks me to load it and hit 'ok' on each one? Why? How do I get it to just print the job without asking me to load an envelope that its already loaded in the MP tray?

Thanks!