missing mimemail_uninstall() to remove all variables

I don't think you just mean disable, you must mean "uninstall". Yup, there's no mimemail_uninstall() implementation, so this module is "leaking" all of its variables:

mimemail_alter
mimemail_crlf
mimemail_engine
mimemail_incoming
mimemail_key
mimemail_textonly

This will be a trivial patch, stay tuned.

Since there's no mimemail.install already existing, here's a raw copy of the new file, instead of a patch. Tested and works as expected. This is RTBC, but it's my own patch, so I'll let someone else decide that. ;)

Works as advertised.

Variable 'smtp_library' is set by mimemail and may have a value like "sites/all/modules/mimemail/mimemail.module". Leaving this variable untouched at uninstall should not cause a problem. drupal_mail_send() handles this correctly.

Thanks for the review. This is still an issue I'm planning to see through to the end, so I'm keeping it assigned to myself. ;)

Committed to HEAD, thanks!