[Plugin: JetPack] "Post by EMail" don't works

I have trying to enable the “Post by E-Mail” functionality of JetPack. But it doesnt work.

What I have done: I have enable The “Post by EMail” function of the JetPack plugin and then I have create a email address “[email protected]” like it was described here: https://jetpack.me/support/post-by-email/#generate-pbe
Then I have send a email to the created address “[email protected]” and I have wait some minutes (> 10 minutes). But nothing happens. The expected post was never added. There is no error message, not in the httpd logs and I have also no error mail received or something else. Whats wrong? Where I can get more error informations?

Thanks a lot,
Steffen