• Every time Mac OS X updates, I get a message that QuoteFix is disabled
• I have installed QuoteFix, but it doesn't seem to be working?
• Why doesn't QuoteFix always remove the signature of the sender?
• Why does my own signature appear at the top of each reply?

With the introduction of Snow Leopard, Apple added an extra security/stability measure for Mail.app plugins. Each plugin needs to explicitly declare with which versions of Mail.app and Message.framework it is compatible. The idea is that plugins untested for a specific version won't be loaded, hence providing extra security and stability.

Most of the time, these versions change when Apple releases Mac OS X updates. And so, you get a message saying that QuoteFix (along with other plugins you have installed) isn't compatible anymore.

When new versions of the OS arrive, it might take some time for me to update and therefore to check if the plugin still works on the new version. If you're impatient and not afraid of a bit of hacking, you can fix the plugin so it will be accepted again by Mail.app. To do so, follow these steps.

First, find out the new versions of the Mail.app and Message.framework bundles. Fire up Terminal and run the following commands (each on a single line):

defaults read /Applications/Mail.app/Contents/Info PluginCompatibilityUUID
defaults read /System/Library/Frameworks/Message.framework/Resources/Info PluginCompatibilityUUID

NB: with the introduction of OS X 10.9 (Mavericks), you only have to perform this action on Mail.app, and not on the Message framework.

This results in two large strings.

Next, open ~/Library/Mail/Bundles/QuoteFix.mailbundle/Contents/Info.plist in an editor (NB: if Mail.app complained about an unsupported plugin, it moves such plugins to ~/Library/Mail/Bundles (Disabled) so look there if you can't find it) and find <key>SupportedPluginCompatibilityUUIDs</key>.

In the array following that key, add the two UUID strings similarly to the ones already there, save the file, and close it. Move the plugin back to ~/Library/Mail/Bundles/ if necessary.

This should at least make Mail.app stop complaining about unsupported plugins. It doesn't, however, guarantee that the plugin will still function properly with the new versions. So be careful.

As an alternative you could try the MailPluginFix application, although I haven't tested that myself.

The most common reasons for QuoteFix not functioning properly, or not at all (apart from it being disabled after an update of the Apple Mail application), is either bugs (mea culpa!), or incompatibilities with other Apple Mail plug-ins you have installed.

Specifically, some users have reported problems with the Attachment Scanner plug-in (which I haven't been able to reproduce myself, making debugging this problem quite difficult).

If you're adventurous, fire up the Console application and under FILES, select system.log. In case of problems with QuoteFix, that's where some debugging information is logged to which might aid me in finding the problem (please report issues here).

QuoteFix will only remove signatures if they start with the "internet standard" signature separator "-- " (that's hyphen hyphen space, followed by an end-of-line).

The reason for this is that since most e-mail programs (including Mail.app itself) allow users to freely form their own signatures, automatically determining what the signature in the original message is can be near impossible.

Because Mail.app is set to do so :-) (by the way, this setting will also cause the cursor to be placed at the top of the new mail message, irrespective of the setting Move cursor to top of document after QuoteFixing).

You can turn this off by unchecking the Place signature above quoted text option in the Signatures preferences.