Have you checked in your providers web mail. May providers these days do SPAM filtering and they place spam in a spam folder. This is not downloaded for POP mail accounts, and often must be manually subscribed for IMAP accounts.

Matt . . . Thank you for your reply, but not being computer savvy, I don't know how to check these things.

Do you use a Pop or Imap mail account in thunderbird?

right click on mail account name in Folder Pane and select 'Settings' select 'Server Settings' for the mail account At the top on the right side it will say 'Server Type'...POP or IMAP?

TO: Toad-Hall . . . I did what you suggested. I have a POP Server. Now what?

I also reloaded Internet Explorer from Windows web instructions because the default browser in Windows 10 is Microsoft Edge, from which I am unable to access my web e-mail. I checked my Spam folder in Internet Explorer e-mail, and it is empty, too!

Now check the pop mail account Junk Settings.

See first image below as a guide. This sets up what to do on a per mail account basis.

• Right click on mail account name in Folder Pane and select 'Settings'.
• Select 'Junk Settings' for the mail account
• Select: 'enable adaptive junk mail controls for this account'
• Select address books to act as a 'whitelist' ...'do not auto mark as junk if sender is in a selected address book.

under Destination & Retention

• select 'Move new junk messages to'
• select 'Junk folder on:' and pop mail account name

• I prefer to empty junk each day after checking , but if you want it auto emptied: select 'Automatically delete junk older than xx days'

• click on 'OK'

Then check Junk Options - this is a global preference effecting all mail accounts. see second image as guide.

• 'Menu icon' > 'Options' > 'Options' > 'Security' > 'Junk' tab
• Select: 'When I mark messages as Junk'
• Select: 'Move them to the account's 'Junk folder'

I prefer not to auto mark junk as read, just in case I want to mark a good email as 'Not junk', so it gets moved back to Inbox still unread. It also means the Junk folder stays bold reminding me to check at end of day before emptying and then compacting to remove all traces. But this preference is up to you.

• if you want junk marked as read automatically...select 'Mark messages determined to be Junk as read'

It is worth enabling the logging just in case you ever need it.

• Select 'Enable adaptive junk filter logging

The 'Reset Training Data' button is only used if something goes awry and you need to clear old data and start training afresh.

• click on 'OK'

Thunderbird will now need to be trained so that it learns what you call Junk and Not junk. If you get messages in 'Junk' that are good emails, you need to select that email and click on the 'Not junk' button. Equally, if you get junk emails in 'Inbox', you need to click on the 'Junk' button. After a while Thunderbird soon learns what to do, although the odd email may get put in the wrong place. I have found it works rather well.