We've all experienced the embarrassment of sending someone an email referencing an attached file or document, only to receive a reply that, despite our claims, nothing was attached. It's a frequent-enough problem that a few years back, Google added a feature to Gmail that would alert you if you forgot to attach a file referenced in your message.
Though OS X's Mail app doesn't include this convenient feature, ChungwaSoft's $6 ForgetMeNot is a nifty mail plug-in that seamlessly adds it. Install ForgetMeNot, and whenever you attempt to send a message using Mail, the plug-in first scans the text of that email for specific words indicating that you meant to include an attachment. If ForgetMeNot detects one of those words and the message indeed includes an attachment, the message goes through; if the message is missing attachments, you see an alert. You can then choose to cancel sending, add the attachment, or send sans attachment.
ForgetMeNot includes default keywords for each of seven languages: Dutch, English, French, German, Italian, Portuguese, and Spanish. For example, for English, the plug-in watches for the words attachment, attaching, attached, and attach. You can also add your own words to a language's list--I've added image, images, file, and files to the English group--and you can disable languages you don't use. However, you can't add new languages: To add a list of keywords in a different language, you must add those words to one of the supported languages (which means ForgetMeNot will use that language's stock keywords in addition to the keywords you add).
ForgetMeNot's keyword-based intervention generally works well, although it's of course limited by the list of words it watches for. If your message says "Check out this hilarious photo of Nancy!" and you haven't added photo to the list of keywords, ForgetMeNot won't alert you if you forget to include a hilarious photo of Nancy.
I also have one technical complaint: The ForgetMeNot installer places the plug-in, ForgetMeNot.mailbundle, in the main Mail plug-in folder (/Library/Mail/Bundles), where it affects all users' accounts, rather than in your personal folder (~/Library/Mail/Bundles), where it would affect just your account; if you manually move the plug-in to your personal Bundles folder after installation, ForgetMeNot no longer works. ChungwaSoft should at least offer the option to install the plug-in in your user folder--or, even better, just install it there by default.
That quibble aside, ForgetMeNot is a nice add-on for Mail that will inevitably spare you some embarrassment.
Sign up for CIO Asia eNewsletters.