Q/ I get emails from some people but others complain that I do not get email from them, what could be the problem?
Answer:
This sometimes happens when your hosting accounts disk quota is more than 90% consumed or your email accounts quota is more then 90% consumed.
in this case you will get some emails until your quota is consumed, and any others will sit in the mail queue, until you have downloaded your email and have made some disk space free, after which the emails that are sitting in the mail queue will be delivered if there is sufficient disk space to store them in your account, if not those that can be delivered will be and the others will sit in the mail queue.