After an update from an older version to a MailCheck version 4.5.x
or higher, this function is not automatically available. To activate this
function, you will have to log out and then log in
again all email accounts. Afterwards, the function will be fully available
to you in GMX
MailCheck, move your mouse over an unread email that you want to delete.
A trash symbol appears.
To delete your unread email, click on the trash symbol.