If you have exceeded the space in your e-mail account the message will not lead you to a place to request having more quota space and requiring you to give your password and other private information on a form. The message will be from your provider and will not say how to increase quota space (they have the same quota for all the same type customers) but tell you to delete messages and make space. Make sure you empty not just in the trash and inbox, but also the outbox/sent)
The message you are probably looking at is spam and is a phishing email wanting your account information including password. The ones I have seen have not identified your email provider; webmail is not an email provider. Do not reply to these. If you did, immediately contact your ISP and e-mail providers and any banks/credit cards you may have given account information of and also law enforcement so they can be blocked from stealing from you.
These are just the latest version of the various phishing emails. Many of them fit in the category of you have unclaimed funds or appear to come from a bank but may be either a bank you never heard of or that you have never done business with. Quite often the grammar is horrible or spelling is wrong, I still like the one I got from the Bank of America supposedly that spelled America consistently as Amerca.
If the message was really from your email provider or your bank they will include your actual name in the email, not just a general email that says your account has problems and no mention of who you are. Your bank knows your name.
Many of the e-mail providers now such as Yahoo, Gmail (Google), Hotmail (Live/Microsoft) either provide unlimited space or the quota is so big it is doubtful you would exceed it.