Same here, I just retested it and now it works again.
Without me changing anything whatsoever.
Seems something between wp5.6 and cf7 5.3.1 was screwed up and got somehome fixed in the background.
Happy that it works again. Would be nice to know what might have caused it.
Cheers,
Dom
Takayuki-san,
I also get the red error message when trying to send the email.
This error only occured after updating to the newest version of contact form 7 and also to wordpress 4.6 this morning
It worked fine for months before under the previous versions of cf7 and wp.
Can you please check.
This seems to be an issue with on plugin/wp side and not on the user setup side.
Arigatô!
Dominik
