If you find that you are unable to send email using the Mail client in Windows 8.1 (for example, the mail sits in the outbox and never reaches the recipient) it is likely that you need to make a small change in the configuration settings for your email account.
To do this, open your Mail client and move your mouse to the bottom right hand corner of the screen to open up the charm bar. Select Accounts.
Select your Gradwell Cloud email account and look for the entry for Outgoing email server. Ensure that this is set to smtp.gradwellcloud.com and that the port is set to 587.
This is different to the default port that the Mail client uses, and if it isn't set to port 587 you will be unable to send email.