[otrs] Disable HTML mails

Hello. I've just installed an OTRS and it's really impressive tool and it seems to fill our needs quite perfectly. However there's a small feature which I couldn't turn off, so is it possible to configure OTRS to use only plaintext mails instead of html ones? HTML doesn't give us any additional perk and most of the times it's more annoying than useful. Ie. we'd like to use an SMS-gateway for one of our queues, but currently we get the HTML-tags in SMS as well. TIA. -- Take