This has resolved for me. My guess is that it was due to a restore from an out of date image. The same thing has changed my debit details as outlined in a separate thread.
I'd say that it was coincidence in your case as it was affecting at iOS and Windows mail clients for many users, it now looks resolved across all platforms.
The email issue was raised with our system administrators and have confirmed that everything should be working properly now.
Should this not be the case, please don't hesitate to send us a private message in order for us to assist accordingly.