How to configure SMIME on Zimbra

How to configure S/MIME(Webmail, ZCO,IMAP,POP and Thunderbird)?


   KB 24294        Last updated on 2021-06-2  




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What is S/MIME?

S/MIME is an acronym for Secure/Multipurpose Internet Mail Extensions. It references a type of public encryption and signing of MIME data (email messages) to verify a sender’s identity.

What it allows you to do is two things:

Ensure to your email recipients that YOU actually sent the email.

Allows the possibility of sending and/or receiving email encrypted.

How Does S/MIME Work?

As mentioned above, S/MIME is a type of “end-to-end” encryption solution used for email messages. To be more specific, it uses asymmetric cryptography to protect emails from being read by a third party.

Sign: Digitally validate that you are the sender of a message. When signing, you use your private key to write message's signature, and they use your public key to check if it's really yours.

Encrypt: encrypt the composed message for one or more recipients. When encrypting, you use their public key to write a message and they use their private key to read it.

In order to encrypt, you must have previously received a signed message from that user, such that Zimbra has stored the public S/MIME certificate for that other user. A digital id or digital certificate consists of a public and private key. Your public key is shared with everyone. Your private key is kept private.

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