A new feature of Mail in El Capitan is the ability to swipe across a message using your Mac's trackpad to access some common functions. This is similar to how Mail in iOS works. You can mark a message as Read or Unread, or delete it. You can also change the delete option to archive. This even works for messages not currently selected.
When you compose a new message in Mail, you are usually spending a very short amount of time in the Mail composition window and it is easy to miss some of the features. At the top of the window you can use various buttons and add more. You can also change the fields available to you, such as adding or removing CC and BCC fields and even a REPLY-TO field. In the message body area, you can use styling and also mark up images and PDFs.
Text Replacement is a built-in function on your Mac that allows you to automatically replace one sequence of characters with another. You can use them to fix common typos, make it easier to type long phases, or even allows you to insert longer passages you commonly use when writing. They can also help when trying to type special characters or emoji. Text Replacement works in most apps though some have special settings.
You can filter junk mail in the Apple Mail app, but you should first try to prevent spam email from even getting past your server. If you use a good transportable email address, like Gmail, you'll get most of your junk mail filtered out before it gets to your Mac. Apple Mail can act as a last line of defense if you set up junk mail filtering in the preferences. You can also add your own filters for reoccurring spam email in Gmail and in Apple Mail. If you no longer want to receive mail from a company you have done business with or have subscribed to, be sure to use their Unsubscribe button instead of reporting the email as junk.
With OS X Yosemite you can mark up images and PDF files right inside of the Mail composition window. This can make it easy to send notes and revisions back and forth between people working on projects. You can also add signatures to PDFs easily in a reply. The same tools are available in the Preview app outside of Mail. In the future, Apple and third-parties can add more extensions like Markup.
When you reply to a message in Mail, you can quote the original message to make your reply clearer. You can quote the entire message, but it usually make more sense to only quote a portion of it. You can also edit the quotes and place your reply between portions of quoted text. Learning how to use quoting properly can help you send more concise, clear and professional email replies.
An often-requested feature of Mac Mail is the ability to tag messages with keywords. While full tagging ability isn't included in Mail, you can add colored flags to messages to help you organize them. You can even rename the flags to make them more useful. But for true tagging ability, you would need a third-party extension like MailTags.
When you type a quote or apostrophe symbol on your Mac, it will usually automatically convert to the curly version. However, you can control when this happens on a per-app basis. You can also make exceptions to the process while typing. See examples in TextEdit, Pages and Mail.
Learn about some of the actions in Automator that control the Calendar and Mail app. Build a workflow that will search your events, summarize them as text, and convert that text to an audio file. Then Mail can send it as an email message.
Using the Mail app on your Mac you can get a special alert when an email from a specific sender arrives. This can be a sound, notification, icon bounce or even a special color for the email in your inbox. To do this, learn to use Mail rules. A rule can identify a new message and then apply an action to it. You can also have messages forwarded to another email address.
You can type Emoji characters on your iPhone, iPad or Mac and add them to your text messages, email messages or documents. Emoji characters are color characters with small images like smiling faces, map symbols, hearts, and so on. On the iPhone and iPad you need to enable the Emoji keyboard to easily type these. On the Mac, you need to turn on your character viewer.
Mac Mail has a feature that allows you to use colorful email templates. There are many to choose from, and you can buy more from third-party companies. You can also create your own through a variety of methods.
Mountain Lion adds the ability to recognize senders of email as VIPs. Once you indicate that someone is a VIP, their email will also appear in a special inbox just for them. You can view all VIP email at once, or just one VIP, or your regular inbox as before. You can also customize Mail so it only notifies you when you get a new email from a VIP, not just everyone.
In OS X you have various ways of setting default applications for files and other actions. You can set your default email and web browser applications with settings in Mail and Safari. You can set what happens when you connect a camera or SD card, or insert an optical disc. You can also set which application will be used to open specific file types.
Performing quick by complex searches in the Finder and in Mail is easier in Lion because of the new search tokens feature. You can build queries using text, dates and file types right in the search field.
You can assign rules to keyboard shortcuts with the Mail extension Mail-Act On. This makes it easy to send messages to folders without your hands leaving the keyboard. You can also assign rules to outgoing messages and alter how Mail sets the read status of messages.
You can add functionality to Gmail using Gmail Labs extensions. Take a look at some of the most useful extensions, like Multiple Inboxes, Superstars, Canned Responses, Inserting Images and Undo Send.
A common request is to include a small image in Apple Mail email signatures. This isn't easy to do, but there is a trick that can be applied to get a small image added to your signature.
Gmail is often the choice of email power users. You can optimize your Gmail experience even more by learning some simple keyboard shortcuts that allow you to navigate, read and compose email without having to move your fingers from the keyboard.
You can use Rules in Mail to create autoresponders that will instantly reply with an automatic message when you get email. You can tailor the autoresponders to reply to messages with certain subjects, from people or domains or to special email addresses.