Q/ Why isn't email arriving in my email account ?
Answer:
This can happen when you keep email stored in your email account, consuming all of the allocated email quota. Additional email will sit in the mail queue for 7 days attempting delivery to you email account, this will not succeed until there is enough disk quota available, to store the email
This can also be caused, by your hosting account having used all of it's available disk quota, so even if your email account has unlimited disk quota, but the hosting account has no disk space left, the result is the same as above, if there is no space to store the email then it cannot be delivered.