How to make un deletable only mail

A clever question!

Unfortunately, it's not possible to create an "undeletable" email that cannot be deleted by the recipient or their email provider. Email is a decentralized system, and once an email is sent, it's up to the recipient to decide what to do with it.

However, there are some creative ways to make an email more "persistent" or difficult to delete:

  1. Use a secure email service: Consider using a secure email service like ProtonMail, Tutanota, or Mailfence, which offer end-to-end encryption and can help protect your emails from being deleted or accessed by unauthorized parties.
  2. Use a digital signature: You can use a digital signature tool like S/MIME or PGP to sign your email, which can help verify the authenticity of the email and make it more difficult to alter or delete.
  3. Use a tracking pixel: You can add a tracking pixel to your email, which will allow you to track whether the email has been opened or deleted. This can help you determine if the recipient has intentionally deleted the email.
  4. Use a "read receipt": Some email providers offer a "read receipt" feature, which sends a confirmation email to the sender when the recipient opens the email. This can help you determine if the recipient has read the email, even if they delete it later.
  5. Use a third-party service: There are third-party services like Email Archiving or Email Retention that can help you store and preserve your emails, even if the recipient deletes them.

Keep in mind that even with these measures, there's no guarantee that the email cannot be deleted. The recipient can still delete the email, and it's up to you to ensure that you have a backup of the email or other evidence of its existence.

In summary, while it's not possible to create an "undeletable" email, you can use various techniques to make your emails more secure, trackable, and persistent.