Additional utilities can enhance Mac OS X Mail with functionality and features: strong encryption, for example, or message priorities.
QuoteFix has Mac OS X Mail start your reply at the bottom in a proper fashion. (Mac)
A to G converts your Mac OS X Address Book to a CSV file, used by many email clients to import contacts, in a most simple and useful manner.
Address Book Importer is a fantastic utility to import contacts from CSV files (to which every respectable email program or service exports) into the Mac OS X Mail Address Book with ease and elegance.
Attachment Scanner Plugin for Mail alerts you when you talk about a file attachment in a message but failed to attach any file before clicking "Send".
emlx to mbox Converter is as straight forward a tool for exporting Mac OS X Mail messages to the universal mbox format as it can be a godsend if, after a disk crash for example, you have to recover your mail and Mail refuses to import its own emlx files.
equinux Stationery Pack makes it easy to add hundreds of gorgeous stationery designs to Mac OS X Mail — and helps you find the perfect template for the occasion, too.
gMailContacts swiftly imports names and email addresses from your Mac OS X Mail address book into Gmail. (Mac)
GPGMail adds strong OpenPGP/MIME email encryption to Mac OS X Mail.
Integrating well with Mac OS X Mail, httpmail lets you access a Hotmail or MSN email account with all the comfort of Mail.
IMAP-IDLE for Mail.app adds support for the IMAP IDLE command to Mac OS X Mail, which means new messages come in as soon as they arrive at the server without any manual or periodic mail checking.
LinkABoo lets you place links to individual Mac OS X Mail messages on the Desktop, in the Dock or in just about any application including data organizers and calendars.
Mail Act-On is a wonderful Mac OS X Mail plug-in that saves you time and makes your mail handling better by allowing you to assign keyboard shortcuts to Mail rule actions (and adds outgoing mail filters to boot).
Mail Attachments Iconizer makes all attachments show as space and time saving icons in Mac OS X Mail.
Mail Stamps replaces the icon set introduced with Mac OS X Mail 2.0 (Tiger) with the toolbar icons found in Mail 1.3 (Panther).
Mail Type Select jumps to messages in Mac OS X Mail as you type (part of) the subject, sender or recipient.
Mail2iCal and Mail2iCalToDo are highly useful AppleScript applications that let you turn any email from Mac OS X Mail into a calendar or to-do list item in iCal swiftly and with all the essential data (including URLs and attendants) entered.
Mailboxer picks up the contacts in your Address Book and sets up corresponding smart mailboxes in Mac OS X Mail, each listing all mail exchanged with the person (no matter the email address, if they have more than one).
MailFollowUp lets you create followup messages that have all the recipients of the original message and quote the original text easily in Mac OS X Mail.
MailPriority adds support for message priorities to Mac OS X Mail, and it lets you request (albeit not send) return receipts, too.
MailSwitch is a nice and useful utility if you want multiple people to use Mac OS X Mail, but don't want to go through the log-out/log-in procedure every time.
MailTags lets you add tags, keywords notes and due dates to emails in Mac OS X Mail and integrates them with both search, rules and smart mailboxes for near-perfect and semi-automatic custom email organization.
MailTemplate adds useful templates to Mac OS X Mail and Entourage. Thanks to several macros it is quite flexible.
ManilaMail counts the number of unread messages in your Mac OS X Mail Inbox, and offers easy access to that Inbox as well as to composing mail to boot.
MiniMail shrinks Mac OS X Mail to a handy window displaying just one message and useful ways to interact with it.
MsgFiler and its folder selector that finds the right mailbox if you type but a few characters in its name make moving messages particularly smooth and easy in Mac OS X Mail.
OMiC makes Mac OS X Mail handle winmail.dat inclusions as if it had invented them, making included files and rich formatting available just like other attachments.
Subjectivity warns you when you are about to send an email with a blank Subject: line from Mac OS X Mail and can insert your message's first words in it automatically.
VacuumMail ensures your Mac OS X Mail is always running at top speed by keeping its database organized and slim, even on an automatic schedule.
