Are you able to send emails but not receive?
Most likely your domain's allowed disk usage is over quota, or your e-mail address itself is over quota. You will need to increase the amount of disk space to receive mail again.
If you are on cPanel (Linux) account
Please sign into cPanel and look in the left menu for Disk Space Available. Make sure this is a positive number.
Next, please, click the Email Accounts icon. Check the column that says Usage, and make sure it is not higher than the Quota.
If you are on Plesk (Windows) account
Please sign into webmail at http://webmail.yourdomain.com. Click on My Today Page and on the right pane under Disk Space limits make sure your Currently used value is less than Limits value.
How can the email go over quota?
Email account tends to go over quota if the last message was large or if you have been storing emails on webmail for a quite some time and eventually your assigned quota has been overused.
What should I do if I am over quota?
If you are over quota best thing is to sign-in to webmail and start removing unncessary emails. Alternatively, configure an email client such as Outlook and download all your emails to you PC. See guide to configuring email clients here.
If you still have problems, please contact HostBreak support via help desk.