Anyone who has been able to send mail with attachments from a iOS app and use the MS Outlook app and not the built-in mail client on an iPhone?
If you are using the MFMailComposeViewController, this is via the default mail client. There is no way to send emails on behalf of the user outside of the Outlook application. With the CanSendMail function you can detect if the user has an active mail on the default mail client. If this is not the case, then you need to open the application that is linked to a custom protocol: