What does "Send Encrypted" do?
If you have the Premium Service, you can send password- or PGP-encrypted messages when you compose on Mailshell's site. To do this, check the "Send Encrypted" box when composing the message. When you send the message, you will be prompted for additional information:
- If you wish to use password encryption, enter a password, an optional hint that the recipient can use to guess the password, and an expiration time. When the recipient receives the encrypted message, they will see the hint (if given) and be asked to enter the password before they can view the message. Once the time you have selected has elapsed, the message will be automatically deleted.
- If you are sending to a single recipient and that recipient has a registered PGP key, you have the additional option of using PGP encryption instead of password encryption. If the recipient has more than one registered key, use the menu to select the key you wish to use (normally, the most recent key is the best one to choose).
Click the "Send" button when you are done.
If you have chosen password encryption, your recipient will receive an email asking them to enter your password before they can then view the message. If you have chosen PGP encryption, your recipient will receive the encrypted message and will need to decrypt it using their own software.
If you have the free trial service, this feature is available during the 30-day trial period after you first sign up. Once that period has expired, you can upgrade to the Premium Service to continue using it.
Please note: For security reasons, if you choose PGP encryption and are saving the message in your Sent folder, the message will be stored encrypted; you will not be able to decrypt it to view its contents. Also note that you can't add attachments to encrypted messages.
Why can't I send attachments with encrypted messages?
Mailshell currently doesn't offer the ability to encrypt more than a basic message--i.e., one that consists only of a header and body. If you have added attachments to a message, the encryption feature will be disabled for that message.
What is PGP encryption?
PGP (Pretty Good Privacy) is the industry standard for encryption technology and is much stronger than simple password encryption. The PGP system consists of two matched keys for each individual: a public key (stored on accessible central key servers and used for encryption) and a private key (stored by individuals and used for decryption). To send a PGP-encrypted message, you use your recipient's public key to encrypt it, and your recipient would then use his or her corresponding private key to decrypt it. (For instance, if you wanted to send a PGP-encrypted message to firstname.lastname@example.org, you would encrypt it using the public key for email@example.com; he would then decrypt it using the private key stored on his personal computer.)
Mailshell's Premium Service lets you send PGP-encrypted messages to single email addresses that have registered public keys. You can learn more about PGP, including how to download the free cryptographic software and create your own public and private keys, at the MIT distribution center or Gnu Privacy Guard.
How can I get my own PGP keys and software?
If you wish to receive PGP-encrypted messages, you can download the free cryptographic software used to create key pairs and encrypt and decrypt messages from the MIT distribution center or Gnu Privacy Guard.
I received a PGP-encrypted message and don't know how to decrypt it. What do I do?
Mailshell users can only send PGP-encrypted messages to email addresses that have a public key available on one of the public key servers--so at some point, a key was created for your email address with a private (decryption) key stored locally. If you do not have the software that stores the corresponding private key and lets you decrypt messages (e.g., PGP Freeware or Gnu Privacy Guard), you will be unable to read the message. You can do one of two things:
- Reply to the sender and ask him or her to re-send the message using no encryption or password encryption instead.
- Download the software, create a new public key, and upload the new key to a key server, then ask the sender to re-send the message using the new key.
If you do have the software, you should refer to that program's documentation for help decrypting the message.