Is this a scam?

I got an email to say that my storage is full at 100% and that I need to deleted my cache. There was a link to click on, but I did not not trust that and the email is now deleted.
How do I delete cache please?

Well, if it is a genuine message, it will come from your email provider. Please check with them if your quota on the mail server is full. If it is, you will need to delete some messages to make space.

If you need to keep the messages, you can move them in eM Client to Local Folders. This will keep a copy in eM Client, but remove them from the server so free up space there. If Local Folders are not visible below your other folders, you can enable them by selecting Menu > Settings > General > Folders > Local Folders. Click on Save & Close to save the setting.

If it is a problem this happens regularly, you can use eM Client’s Automatic Archiving to move older messages automatically. The Documentation (F1) explains how to set that up.

Thanks. There is no way to speak/contact anyone to ask as I am on the free version.

My messages are already in the Local Folders.