You might be using your e-mail a lot for sending and receiving attachments, so you will not be surprised if the limit is sometimes reached.
However, watch out for an e-mail that is warning you about your e-mail exceeding its maximum limit and sounds like this:
"Dear subscriber, this is to inform you that you have exceeded your e-mail quota limit. You need to increase it, otherwise your e- mail account will be disabled in 24 hours. Increase your e-mail quota limit now and continue to use your account.”
By following the link that the scammers provide, you give personal info, starting with your e-mail password.
How to avoid: in personal messages, if you are approached with “dear subscriber” instead of your real name (also look for bad grammar), you can bet it is a scam.