How to use a Digital ID (sign and encrypt messages) in email client?

You have configured your email client to use a digital ID to sign and encrypt email massages. But before using it, it is necessary to understand some important things about public key cryptography.

If you have your digital ID and a private key associated with the digital ID , then you are able to send digitally signed email messages to your friends and receive encrypted messages from them.
 
A digitally signed message contains:
 
1. A message subject and body
2. A digital signature of the message
3. Your digital id with your email and your public key.
 
There are two types of keys used in email encryption:
 
1. Your private key – this key is used when you sign your message and decrypt the encrypted messages received from your friends
2. Your public key – is used by your friend (or any other person) to verify your signature and to encrypt a message for you.
 
Thus, your friend will be able to encrypt messages he sends to you only after he receives a digitally signed message from you once. This means that your friend will use your public key that is in your digital ID to encrypt email messages for you. And only you will be able to decrypt these messages using your private key (secret key).
 
In other words, if you want to get encrypted messages from your friend, then send a digitally signed message to him once. After that your friend should add your digital ID from your email to his address book (usually it's enough to simply add your contact to his address book).
 
On the other hand, if you want to send an encrypted message to your friend, then he should send you his digital ID. After that, you will be able to encrypt email messages for him using his public key that is in his digital ID. And only your friend will be able to decrypt these messages using his private key (secret key).
 
Therefore, if you have your digital ID and a private key associated with the digital ID and you have a digital ID of your friend, you are able to send encrypted and digitally signed messages to your friend. In other words, you and your friend should send a digitally signed message to each other once and add the digital IDs (normally, contacts) to your address books.
 
To sign and/or encrypt a message in Outlook or Outlook Express you should open a new mail message window, type your new message subject and body, click the "Digitally sign message" button and/or "Encrypt message" button on the top of the new message window. After that, you may send the message and it will be digitally signed and/or encrypted.
 
Besides, if you have your digital ID and a private key associated with the digital ID you may simulate the email exchanging that is described above (to test how it works). You may send a digitally signed message to yourself (to the same email), add your received digital ID to your address book, reply with encrypted and signed message to yourself (to the same email) and receive and decrypt this message. In other words, you may send digitally signed and encrypted messages to yourself instead of sending them to your friend.