I’ve used Mail.app before. Several years ago, when my volume of mail grew too great to manage it easily in mutt or pine, I switched to Mail.app. My favorite feature from it was the fast, accurate searching. If the search string appeared in any message, anywhere in my mail folders, it would find it quickly. (It was certainly slower to search the entire collection than a single folder, but still perfectly usable.) It also handled multiple identities better than pine (mutt didn’t handle multiple identities at all then, it may now).
I stopped using Mail.app late last year when it ground to a screeching halt under the weight of my email. At 3GB of mail across all my folders, it was taking a minute or more to load a single folder. I also didn’t like the fact that Mail.app moved away from mbox format for storage, because before the change I had been happily accessing the same mail folders from both pine and Mail.app.
So, last week I installed MailTags and then loaded up one of my IMAP accounts into Mail.app, to get a nice sized collection of email to play with (this particular account has about 3000 messages between the inbox and IMAP folders).
MailTags acts as a plugin for Mail.app. It adds a new panel to the main window and a few additional menu items. It allows you to annotate messages with meta information such as keyword tags, a project, a text note, and a scheduled todo entry. The MailTags panel lets you create iCal Todo entries without leaving Mail.app, which is a nice work-flow boost (though it would be nicer if it could create full calendar entries).
If you have an average volume of email and want a more feature-rich archival system, MailTags could work well for you. Setting tags is a manual process, so it’s not usable for me. (Anything that adds extra work to the email process is more than I can manage.)
A further downside for me: It’s Mac-only, so I can’t use it from my Linux desktop. I switch from desktop to laptop quite frequently, so I like to have my email available no matter where I am. Also, the tags are only client-side, so if I set the tags in IMAP on one Mac, they don’t appear in Mail.app on another Mac.
On a related note, Mail Act-On from the same company as MailTags, adds nifty keyboard short-cuts to Mail.app. This solves another problem I have: I spend an enormous amount of time clicking around and dragging messages. Even though the GUI is better for managing large volumes of email in many ways, it’s also slower than I used to be with mutt key-commands.