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---
stage: Enablement
group: Distribution
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
---
# Signing outgoing email with S/MIME
Notification emails sent by GitLab can be signed with S/MIME for improved
security.
Be aware that S/MIME certificates and TLS/SSL certificates are not the
same and are used for different purposes: TLS creates a secure channel, whereas
S/MIME signs and/or encrypts the message itself
## Enable S/MIME signing
This setting must be explicitly enabled and a single pair of key and certificate
files must be provided:
- Both files must be PEM-encoded.
- The key file must be unencrypted so that GitLab can read it without user
intervention.
- Only RSA keys are supported.
Optionally, you can also provide a bundle of CA certs (PEM-encoded) to be
included on each signature. This will typically be an intermediate CA.
WARNING:
Be mindful of the access levels for your private keys and visibility to
third parties.
**For Omnibus installations:**
1. Edit `/etc/gitlab/gitlab.rb` and adapt the file paths:
```ruby
gitlab_rails['gitlab_email_smime_enabled'] = true
gitlab_rails['gitlab_email_smime_key_file'] = '/etc/gitlab/ssl/gitlab_smime.key'
gitlab_rails['gitlab_email_smime_cert_file'] = '/etc/gitlab/ssl/gitlab_smime.crt'
# Optional
gitlab_rails['gitlab_email_smime_ca_certs_file'] = '/etc/gitlab/ssl/gitlab_smime_cas.crt'
```
1. Save the file and [reconfigure GitLab](restart_gitlab.md#omnibus-gitlab-reconfigure) for the changes to take effect.
The key needs to be readable by the GitLab system user (`git` by default).
**For installations from source:**
1. Edit `config/gitlab.yml`:
```yaml
email_smime:
# Uncomment and set to true if you need to enable email S/MIME signing (default: false)
enabled: true
# S/MIME private key file in PEM format, unencrypted
# Default is '.gitlab_smime_key' relative to Rails.root (i.e. root of the GitLab app).
key_file: /etc/pki/smime/private/gitlab.key
# S/MIME public certificate key in PEM format, will be attached to signed messages
# Default is '.gitlab_smime_cert' relative to Rails.root (i.e. root of the GitLab app).
cert_file: /etc/pki/smime/certs/gitlab.crt
# S/MIME extra CA public certificates in PEM format, will be attached to signed messages
# Optional
ca_certs_file: /etc/pki/smime/certs/gitlab_cas.crt
```
1. Save the file and [restart GitLab](restart_gitlab.md#installations-from-source) for the changes to take effect.
The key needs to be readable by the GitLab system user (`git` by default).
### How to convert S/MIME PKCS#12 / PFX format to PEM encoding
Typically S/MIME certificates are handled in binary PKCS#12 format (`.pfx` or `.p12`
extensions), which contain the following in a single encrypted file:
- Public certificate
- Intermediate certificates (if any)
- Private key
To export the required files in PEM encoding from the PKCS#12 file, the
`openssl` command can be used:
```shell
#-- Extract private key in PEM encoding (no password, unencrypted)
$ openssl pkcs12 -in gitlab.p12 -nocerts -nodes -out gitlab.key
#-- Extract certificates in PEM encoding (full certs chain including CA)
$ openssl pkcs12 -in gitlab.p12 -nokeys -out gitlab.crt
```
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