UTF8 encoding issue with iOs Mail app

With all mails sent with Sendy we're experiencing this very issue: http://stackoverflow.com/questions/5193599/php-utf8-mail-gets-garbled-on-iphone-mail-app

Basically, accented characters (á, é, etc.) and other symbols get replaced by multiple symbols only on iOs mail app. Gmail works fine. The only way around it is to manually replace á, é, etc. with their entities (á, é, etc.).

UTF8 meta tags are correctly specified in the HTML, so the problem is likely that Sendy is missing a certain encoding header when sending e-mails. Is this possible?

Thanks Ben!