In a recent story about simplifying your email system, I mentioned nine plug-ins for Apple Mail that I use to transform it from a fair email client into a much more powerful tool. A number of people have asked me what those plug-ins are, so here's my list. (For even more suggestions, see Maximizing Mail: Add-ons for Mac OS X's Mail.)
Mail doesn't always handle incoming or outgoing attachments the way I like. For example, I usually prefer to see icons rather than inline images, and I want to make sure recipients see attachments the same way I do. Attachment Tamer (Lokiware, $15) lets me customize the way attachments behave to my tastes. Unfortunately, some features aren't yet working in Mavericks, but the developer is working on an update.
Speaking of attachments, problems can occur when attached files are large or when the recipient is using a mobile device. You can work around this problem by copying the file to your Dropbox (or other cloud-storage service) and emailing only a link — but that requires several tedious steps. With CargoLifter (Chungwasoft, $10), you attach files as you normally would, but then the plug-in does everything else for you: uploading the file, creating the link, replacing the file with the link in your outgoing message, and optionally compressing the attachments.
DEVONthink Pro Office's Apple Mail plug-in
If you use DEVONthink Pro Office (DEVONtechnologies, $150) to organize your documents (and I do), this plug-in — included with the app — lets you add any message to your DEVONthink database with a menu command or keystroke.
Part of GPG Suite, GPGMail (GPGTools, free) gives you OpenPGP-compatible encryption and digital signatures for exchanging sensitive email messages. Although Mail offers built-in support for S/MIME encryption, it's complicated to set up and use (for both you and your correspondents). GPGMail makes the process much simpler and friendlier.
Of all the plug-ins listed here, Mail Act-On (Indev, $25) is the one I depend on most. This multipurpose tool lets you file messages in any mailbox using only the keyboard. You can also create rules that work much like Mail's built-in rules, except that they can operate individually on demand, or on outgoing messages. The new Mavericks version also lets you schedule messages for future delivery.
This plug-in (Gregory Welch, free) once served the crucial purpose of ensuring that the To: and Cc: fields were filled in correctly for messages that you'd previously sent but wanted to follow up on. Now Mail automatically addresses such messages correctly when you choose Reply or Reply All, except in one specific case: When you're adding to a conversation in which you were a Cc: recipient, Mail still wants to swap the contents of the To: and Cc: fields when you reply. This plug-in ensures that the original To: and Cc: recipients remain intact.
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