In recent weeks my phone has been unable to send emails from my synced hotmail account. In speaking to my phone network provider they said to delete the email account and set it up again. When I did this it didn't solve it and they said it is Hotmail related and not a phone software issue. I asked if it would be resolved by any Android update but they said to contact my email provider, Hotmail.
My phone is an Android HTC One (first generation) and my email account is on Hotmail.co.uk, synced via pop3 version. I can receive emails ok, but I cannot forward or send new ones. I've had the phone and no problem with emails for just over a year so it's odd it just started and there was no recent firmware upgrades. Any help duly appreciated. This is not an Outlook issue but you have no option in the Category drop-down to mention Hotmail account, not an Outlook account.