How to Send an Encrypted Email: Step-by-Step Guide

How to Send an Encrypted Email: Step-by-Step Guide

With eclipso Mail Europe, you can encrypt an email using either OpenPGP or S/MIME. The recipient needs the corresponding private key to read the message. For encryption to work, your own key or certificate and the recipients' public key material must be available in eclipso.

Important: OpenPGP and S/MIME are different methods. Choose one method per email. Public keys and certificates can be shared; keep your private key and its passphrase secret.
 

• Step-by-Step Guide

  • Step 1: Check your own key
    For OpenPGP, you need your own key pair; for S/MIME, you need a personal certificate. In the From field, select an address for which the corresponding private key material is stored in eclipso. If the encryption option is unavailable, check your key or certificate setup first.
  • Step 2: Open a new email
    Open "New Email" and enter recipients in the To, Cc, or Bcc fields.
  • Step 3: Write the subject and message
    Write your message as usual. Depending on the method, recipients and the subject may still be visible. Do not put confidential information in the subject.
  • Step 4: Turn on encryption
    Enable the "Encryption" toggle below the subject. In the method selector, choose "OpenPGP" or "S/MIME". Recipients must have a matching public key or valid certificate for the selected method.
  • Step 5: Optionally sign the message
    If you wish, also enable "Digitally sign". A digital signature helps the recipient verify the sender and that the message has not been changed. Signing does not encrypt the message; "Encryption" must be enabled for that.
  • Step 6: Check recipient status
    With encryption enabled, the recipient chips show whether key material was found. Green means a matching key is available; red indicates a missing key. Renew an expired key before sending.
  • Step 7: Send and handle missing keys
    Click "Send". For OpenPGP, eclipso checks recipients before sending. If a key is missing, a dialog appears:
    • "Cancel" - return to the message and add or correct the recipients' keys.
    • "Send only to recipients with key" - recipients without a key are removed; the message is sent encrypted to the remaining recipients.
    • "Send Unencrypted" - after confirmation, the entire message is sent without encryption or a signature.
    • "Send Signed Only" - offered only when "Digitally sign" is enabled. The message is signed but not encrypted.
    For S/MIME, eclipso must have a matching certificate for every recipient. If a required certificate is missing, eclipso cannot encrypt the message with S/MIME and reports a sending error.
  • Step 8: Decrypt the message
    The recipient opens the message in an email program that supports the selected method and decrypts it with their private key. Depending on the setup, they may also need the passphrase.

• If the recipient's key is missing

  • Ask the recipient for their public OpenPGP key or S/MIME certificate and store it in eclipso. With S/MIME, the public certificate can also come from a signed message.
  • The recipient's private key is never needed or shared - only the recipient can use it to decrypt the message.
  • OpenPGP keys and S/MIME certificates are not interchangeable. The sender and recipient must use the same method.

• How do I set up OpenPGP encryption in 60 seconds? ↗
• OpenPGP vs. S/MIME - What's the difference? ↗
• What's the difference between signing and encrypting? ↗
• Solving common OpenPGP problems ↗