Deleting a spam message gets rid of that message. It teaches your email program nothing.

Marking it as junk does. Do that, and the program gets better at catching the next one.

Here is where the button is in each program.

Outlook (the classic version, with the ribbon across the top).

Select the message. On the Home tab, click Junk (some versions label it Block). Choose Block Sender to send everything from that address to the Junk folder.

To control how strict the filter is, go to Home, Junk, then Junk Email Options. The levels are No Automatic Filtering, Low, High, and Safe Lists Only. Many installs start on No Automatic Filtering, which means the filter is barely working. Low is a good start. High catches more and also catches some real mail.

Safe Senders is the opposite list. Add people and companies you always want to hear from. Mail from them never goes to Junk.

If something real lands in Junk, select it and choose Not Junk.

New Outlook for Windows.

Open Settings, then Mail, then Junk email. There are lists for Blocked senders and domains, and for Safe senders and domains. Add an address or a whole domain, then Save.

One catch. New Outlook does not support blocking senders for accounts like Gmail, Yahoo, or iCloud that you have added to it. Block lists work on Microsoft accounts. For the others, use the Junk button on the message, or block in that provider's website.

The old Mail app that came with Windows has been replaced by new Outlook, so these are the steps you want.

Thunderbird.

Select the message and click the Junk button, or press J. To undo it, choose Not Junk, or press Shift+J.

Thunderbird learns from what you do. Mark junk as junk, and also mark good mail that landed in Junk as Not Junk. Deleting alone does not train it.

Settings live under the menu (three lines), Settings, then Privacy and Security, then the Junk section. Each account has its own Junk Settings under Account Settings, and those take priority.

Two habits that help in all of them.

Check the Junk folder once a week for mail that should not be there. A bank or a doctor's office can end up there.

Do not block a whole domain you do not recognize. Block the address, or mark it junk and let the filter learn.

One honest limit.

A filter makes spam smaller. It will not make it zero. Spammers change addresses constantly, so a block list only ever catches the last one.

If you would rather not do this alone, I can sit down with you and set it up.

Tomorrow: Part 4, Clearing It Out.