No incoming email at all from any sender
If you are not receiving email from any sender at all, but you can send email, then your email account is probably over quota (FULL).
Please log into your webmail and delete old messages, sent messages and trash. Alternatively, if you are connecting via Outlook or another email client, copy the emails from the inbox (or other remote folder) to a local mail folder.
Your incoming email will start working once you have created space by deleting the old messages currently filling your account.