When you hear the term email content hidden, it refers to the process of obscuring the actual message within an email. This can be done for a number of reasons, such as to prevent someone from reading the email without your permission, or to make it more difficult for automated systems to scan and parse the contents of an email.
There are a few different ways that email content can be hidden. One common method is to embed the message in an image file. This makes it much harder for text-based scanners to read the contents of the email, since they would need to perform optical character recognition (OCR) on the image in order to extract the text.
Another way to hide email content is by encoding it using a technique called Base64 encoding. This converts the data into a series of characters that are not human-readable, but can be easily decoded by computers. This makes it more difficult for people to read the contents of an email, but does not prevent automated systems from being able to parse and interpret them.
Finally, another common method for hiding email content is simply encrypting it with a password. This ensures that only someone who knows the password will be able to read the contents of the message, making it effectively hidden from anyone else.
All of these methods have their own advantages and disadvantages, so there's no one perfect way to hide email content. It really depends on your specific needs and preferences as to which approach is best for you.