I apparently have a free licence activation key and am told that a reminder of this key has been sent to my mailbox. But no email from eMail Client has arrived, either in the eMail Client mailbox or on my email SP’s webmail or on Windows 10 Mail. I have only one email address, which otherwise works normally for all mailboxes.
Go to http://www.emclient.com/lost-activation-key and enter your email address. Another copy will be sent to you. Also, check your spam/junk folder through webmail, just to be sure it is not there.