How to know that someone is in online through mail

I think there may be a bit of confusion here!

It's not possible to know for certain whether someone is online or not just by looking at their email. Email is a form of electronic communication that allows users to send and receive messages, but it doesn't provide real-time information about someone's online status.

Here are a few reasons why:

  1. Email is asynchronous: Email is a store-and-forward system, which means that messages are stored on a server until the recipient checks their email. This means that even if someone is online, they may not be actively checking their email at the same time.
  2. Email clients can be configured to check for new messages at intervals: Many email clients, such as Gmail or Outlook, can be configured to check for new messages at regular intervals, even when the user is not actively using their email account.
  3. Online status is not publicly visible: Unlike social media platforms, email accounts do not typically display a user's online status.

If you're trying to determine whether someone is online or not, you may want to consider alternative methods, such as:

  1. Using instant messaging or chat apps: These apps typically display a user's online status, such as "Available" or "Busy".
  2. Making a phone call or sending a text message: These methods can provide a more direct way to communicate with someone and get a sense of their availability.
  3. Using social media: Some social media platforms, such as Facebook or Twitter, may display a user's online status or last seen timestamp.

I hope this helps clarify things!