My testing seems to show it's viewing the attachments in preview mode on the affected email suppliers - ie. in both Yahoo/Hotmail if you download the attachment and open them, they work fine - if you try to preview or download the preview on the web, it fails. Attachments work fine on my iOS devices.
https://customer.support-ess.com/kb_view.do?sys_kb_id=cb572d02fbe4d21085b6f92abeefdc73 - here's a KB on the issue
There's nothing on the ESS Service Status page to say problems with InTouch ... but ParentPay group have a conflcit of interest in maintaining and resolving issues with InTouch as they are also SchoolComms which I suspect is more profitable and less problematic ..