To configure the IST email service on your iPhone, just follow the instructions at:

https://support.apple.com/en-us/HT201729

And use:

• Email: firstname.lastname@ist.ac.at
• Server: owa.ist.ac.at
• Domain: IST
• Username: ISTUsername
• Password: ISTPassword

You can now choose to sync Mail, Contacts, Calendars, Reminders, and Notes.