How do I stop mail from automatically marking a message as read?

Whoa, I don't know when this happened, but there's now a checkbox under "Viewing" - "Mark As Read Behavior" that you can check as "never"!

You can't. When you click the mail it opens in the preview pane so it is, effectively, opened and assumed read. I use a flag for mails I want to come back to and a smart mailbox that has all the mails with that flag so I can go through them. Alternatively you can put the "Mark Unread" button in the toolbar and use that. Right click the toolbar, click Customize and then drag the closed envelope to the toolbar.

You can put a button in the toolbar that can flag mails. I've renamed one of the flags "ToDo" and set up a smart mailbox (which you can pin to your favourites bar) which shows only new mail and all mail tagged with the "ToDo" flag. Flagged mails stay in the smart mailbox until I unflag them. I use the keyboard arrows to work through the mails and the trackpad to flag them. Once you've dealt with them then you can unflag and delete them. Having said that, this process won't work if you're a habitual putter-offer. You'd be much better getting into the habit of dealing with things straight away. 99% of your mails you should be looking at only once and acting on them immediately.

The pic shows the flag button (Purple) in the toolbar. I've got flags for Travel, online shopping and gigs and smart mailboxes to collect them together. I've also got some rules that flag automatically - e.g. Airline mails get tagged with the Travel flag, ebay gets the Mail Order Flag, and so on.

catnfidl wrote:

This is one of the main reasons I went back to Thunderbird for a while, I don't understand why Apple won't make this an option when we know it's not impossible.

You can let Apple know what you'd like to see here.

The Apple mail app is pretty basic. There are several much better mail clients. And Thunderbird is one of them. My AI search mentioned: Microsoft Outlook, Spark, Canary Mail, Mailspring, and Mimestream. And there are others, more specialized.

This is one of the main reasons I went back to Thunderbird for a while, I don't understand why Apple won't make this an option when we know it's not impossible.