1/ What attachment? — An email may have an attachment in it, but sometimes, annoyingly, it’s not that obvious. One way to see it immediately is to hold down the Control key on your keyboard and click (or Right-Click, if you have that set up on your mouse or trackpad) the list headers(i.e., usually From Subject, Date Received …) above your main message window to add an Attachments category, which will then show up as a little paperclip icon. In this list the number of attachments an email holds will be listed as a number.
2/ The hidden menu — An email you receive that has an attachment in it has a toolbar that’s hidden (above) until you mouse/trackpad-move your cursor over it (below).
This hidden menu even has it’s own little Apple trademark ‘Disclosure Triangle’ (circled, above) that shows more; in this case, an additional, drop-down menu. The choices you see when you drop this (by clicking on that little triangle) will differ depending on what type of attachments you’ve received, but a handy option for images, for example, is Export to Photos. Select that, and the attached pictures will drop right into your Photos Library.
3/ Save attachments — You could also use the above menu to save all the attachments if the email has more than one; it you just want to keep one of the attached items, click its name.
4/ Right-clicking — If you can see the attachment right there in the main body of the email, you can just right-click (or hold down the Control key on your keyboard and click) directly on the image (or whatever) and you’ll get a pop-out menu of options.
5/ Quick Look — You could choose Quick Look from the above-mentioned poppet menu to see a high-definition image of the attachment, or play an audio or movie file, but why when you can just click on the image and tap your spacebar? It’s much quicker, and note this is the standard Quick Look shortcut you should learn anyway.
Extra — You can simply drag and drop visible attachments out of Mail and onto your Desktop, or onto the Photos icon in the Dock to import it that way.
— Why so late? Sorry, I got really busy this morning.
— Why no email tips for Microsoft Outlook? Coz it’s clunky and it sucks, in a nutshell. I can’t believe people still bother with it.