I tested this out on xFi: if my iDevice is assigned to a profile that has parental control turned on, I cannot send email using the default Mail app, although receiving mail seems to be work, albeit slower than usual. If I assign my iPhone or iPad to a profile without parental control, it works.
Using another email app such as Outlook for iOS does not seem to have this problem.
Please advise. I would like to keep the parental control on for these devices but also have the emails working.