NOT a reply - just adding screen snapshot of the issue

email address needs to be in an address book and that address book needs to be selected to act as a whitelist in the Junk Settings for the account. Right click on mail account in Folder Pane and select 'Settings' select 'Junk settings' set up adaptive junk controls and then train Thundrebird to understand what is and what is not junk. see images below as guide: But first you must select that email as 'not Junk'. It is also advised that you do not send emails that mimic the sort of emails sent by spammers. Info link: https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages