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Use a bought SSL certificate

[TOC]

iRedMail generates a self-signed SSL certificate during installation, it's fine if you just want to secure the network connections (POP3/IMAP/SMTP over TLS, HTTPS), but mail clients or web browsers will promot a annoying message to warn you this self-signed certificate is not trusted. To avoid this annoying message, you have to buy a SSL certificate from SSL certificate provider. Search buy ssl certificate in Google will give you many SSL providers, choose the one you prefer.

Get a SSL certificate

Request a free cert from Let's Encrypt

We have another tutorial to show you to request a free cert from Let's Encrypt: Request a free cert from Let's Encrypt.

Buy from a trusted SSL vendor

To buy ssl cert from a trusted vendor, you need to generate a new SSL key and signing request file on your server with openssl command:

!!! warning

Do NOT use key length smaller than `2048` bit, it's insecure.

# openssl req -new -newkey rsa:2048 -nodes -keyout privkey.pem -out server.csr

This command will generate two files:

  • privkey.pem: the private key for the decryption of your SSL certificate.
  • server.csr: the certificate signing request (CSR) file used to apply for your SSL certificate. This file is required by SSL certificate provider.

The openssl command will prompt for the following X.509 attributes of the certificate:

  • Country Name (2 letter code): Use the two-letter code without punctuation for country. for example: US, CA, CN.
  • State or Province Name (full name): Spell out the state completely; do not abbreviate the state or province name, for example: California.
  • Locality Name (eg, city): City or town name, for example: Berkeley.
  • Organization Name (eg, company): Your company name.
  • Organizational Unit Name (eg, section): The name of the department or organization unit making the request.
  • Common Name (e.g. server FQDN or YOUR name): server FQDN or your name.
  • Email Address []: your full email address.
  • A challenge password []: type a password for this ssl certificate.
  • An optional company name []: an optional company name.

NOTE: Some certificates can only be used on web servers using the Common Name specified during enrollment. For example, a certificate for the domain domain.com will receive a warning if accessing a site named www.domain.com or secure.domain.com, because www.domain.com and secure.domain.com are different from domain.com.

Now you have two files: privkey.pem and server.csr. Go to the website of your preferred SSL privider, it will ask you to upload server.csr file to issue an SSL certificate.

Usually, SSL provider will give you 2 files:

  • cert.pem
  • fullchain.pem (some SSL providers use name server.ca-bundle)

We need above 2 files, and privkey.pem. Upload them to your server, you can store them in any directory you like, recommended directories are:

  • on RHEL/CentOS: cert.pem and fullchain.pem should be placed under /etc/pki/tls/certs/, privkey.pem should be /etc/pki/tls/private/.
  • on Debian/Ubuntu, FreeBSD: cert.pem and fullchain.pem should be placed under /etc/ssl/certs/, privkey.pem should be /etc/ssl/private/.
  • on OpenBSD: /etc/ssl/.

Use the bought cert

The easiest and quickest way to use the bought cert is replacing the self-signed SSL cert generated by iRedMail installer, then restart services which use the cert files.

Replace cert files

!!! warning

If you deployed iRedMail with the iRedMail Easy platform, ssl cert files
are stored under `/opt/iredmail/ssl/`:

* `key.pem`: private key
* `cert.pem`: certificate
* `combined.pem`: full chain
  • On RHEL/CentOS:
mv /etc/pki/tls/certs/iRedMail.crt{,.bak}       # Backup. Rename iRedMail.crt to iRedMail.crt.bak
mv /etc/pki/tls/private/iRedMail.key{,.bak}     # Backup. Rename iRedMail.key to iRedMail.key.bak
cp fullchain.pem /etc/pki/tls/certs/iRedMail.crt
cp privkey.pem /etc/pki/tls/private/iRedMail.key
  • On Debian/Ubuntu, FreeBSD and OpenBSD:
mv /etc/ssl/certs/iRedMail.crt{,.bak}       # Backup. Rename iRedMail.crt to iRedMail.crt.bak
mv /etc/ssl/private/iRedMail.key{,.bak}     # Backup. Rename iRedMail.key to iRedMail.key.bak
cp fullchain.pem /etc/ssl/certs/iRedMail.crt
cp privkey.pem /etc/ssl/private/iRedMail.key

Restart network services

Required services:

  • Postfix
  • Dovecot
  • Nginx or Apache

Depends on the backend you chose during iRedMail installation, you may need to restart:

  • MySQL or MariaDB
  • PostgreSQL
  • OpenLDAP

Verify the cert

  • To verify ssl cert used in Postfix (SMTP server) and Dovecot, please launch a mail client application (MUA, e.g. Outlook, Thunderbird) and create an email account, make sure you correctly configured the MUA to connect to mail server. If SSL cert is not valid, MUA will warn you.
  • For Apache / Nginx web server, you can access your website with favourite web browser, the browser should show you the ssl cert status. Or, use other website to help test it, for example: https://www.ssllabs.com/ssltest/index.html (input your web host name, then submit and wait for a result).

See Also