Final answer:
For setting up a digital certificate to sign emails, GnuPG is an open-source solution that enables email encryption and signing by generating a private-public key pair.
Step-by-step explanation:
To set up a digital certificate to sign emails, an open-source option that would be suitable is GnuPG (GNU Privacy Guard). GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880. It allows you to encrypt and sign your data and communications. To create a digital certificate for email, you would generate a key pair consisting of a private key and a public key using GnuPG. After generating the key pair, you can distribute the public key to recipients so they can verify your signature. Key servers can also be used to distribute your public key. When you sign an email using your private key, recipients can use your public key to verify that the email indeed came from you.
Setting up a digital certificate to sign emails can be done using OpenPGP, which is an open-source option that provides encryption and digital signatures for emails.
OpenPGP uses public-key cryptography to sign emails, ensuring that the recipient can verify the authenticity of the sender.
By generating a public-private key pair, the user can sign their emails with their private key, and recipients can verify the signature using their public key.