What is greymail?

I don't know what GreyMail is. Is it a feature of Tb or could it be spam?

I have used Thunderbird for a long time and have never seen anything named Greymail. Where are you seeing it? Is this a folder or something else? If it is a folder you can always select 1 message in that folder and then press control+a to select all. The press delete.

GreyMail is a message that comes to my inbox, like a spam report. We just started receiving it and I wondered if it, itself, is spam.

Thank you.

It might be something that your email provider is sending you. I would ask them. Like I said I have never seen such a thing in Thunderbird.

read the definition of grey mail http://en.wikipedia.org/wiki/Graymail_%28email%29