Email server setup script

I wrote this script during the grueling process of installing and setting up an email server. It perfectly reproduces my successful steps to ensure the same setup time and time again, now with many improvements.

I’m glad to say that dozens, hundreds of people have now used it and there is a sizeable network of people with email servers thanks to this script.

I’ve linked this file on Github to a shorter, more memorable address on my website so you can get it on your machine with this short command:

curl -LO lukesmith.xyz/emailwiz.sh

When prompted by a dialog menu at the beginning, select “Internet Site”, then give your full domain without any subdomain, i.e. lukesmith.xyz.

This script installs

• Postfix to send and receive mail.
• Dovecot to get mail to your email client (mutt, Thunderbird, etc.).
• Config files that link the two above securely with native log-ins.
• Spamassassin to prevent spam and allow you to make custom filters.
• OpenDKIM to validate you so you can send to Gmail and other big sites.

This script does not

• use a SQL database or anything like that.
• set up a graphical interface for mail like Roundcube or Squirrel Mail. If you want that, you’ll have to install it yourself. I just use isync/msmtp/mutt-wizard to have an offline mirror of my email setup and I recommend the same. There are other ways of doing it though, like Thunderbird, etc.

Requirements

1. A Debian or Ubuntu server. I’ve tested this on a Vultr Debian server and one running Ubuntu and their setup works, but I suspect other VPS hosts will have similar/possibly identical default settings which will let you run this on them. Note that the affiliate link there to Vultr gives you a $100 credit for the first month to play around.
2. A Let’s Encrypt SSL certificate for your site’s mail. subdomain.
3. You need two little DNS records set on your domain registrar’s site/DNS server: (1) an MX record pointing to your own main domain/IP and (2) a CNAME record for your mail. subdomain.
4. A Reverse DNS entry for your site. Go to your VPS settings and add an entry for your IPv4 Reverse DNS that goes from your IP address to <yourdomain.com> (not mail subdomain). If you would like IPv6, you can do the same for that. This has been tested on Vultr, and all decent VPS hosts will have a section on their instance settings page to add a reverse DNS PTR entry. You can use the ‘Test Email Server’ or ‘:smtp’ tool on mxtoolbox to test if you set up a reverse DNS correctly. This step is not required for everyone, but some big email services like Gmail will stop emails coming from mail servers with no/invalid rDNS lookups. This means your email will fail to even make it to the recipients spam folder; it will never make it to them.
5. apt purge all your previous (failed) attempts to install and configure a mail server. Get rid of all your system settings for Postfix, Dovecot, OpenDKIM and everything else. This script builds off of a fresh install.
6. Some VPS providers block mail port numbers like 25, 933 or 587 by default. You may need to request these ports be opened to send mail successfully. Vultr and most other VPS providers will respond immediately and open the ports for you if you open a support ticket.

Post-install requirement!

• After the script runs, you’ll have to add additional DNS TXT records which are displayed at the end when the script is complete. They will help ensure your mail is validated and secure.

Making new users/mail accounts

Let’s say we want to add a user Billy and let him receive mail, run this:

useradd -m -G mail billy
passwd billy

Any user added to the mail group will be able to receive mail. Suppose a user Cassie already exists and we want to let her receive mail too. Just run:

usermod -a -G mail cassie

A user’s mail will appear in ~/Mail/. If you want to see your mail while ssh’d in the server, you could just install mutt, add set spoolfile="+Inbox" to your ~/.muttrc and use mutt to view and reply to mail. You’ll probably want to log in remotely though:

Logging in from Thunderbird or mutt (and others) remotely

Let’s say you want to access your mail with Thunderbird or mutt or another email program. For my domain, the server information will be as follows:

• SMTP server: mail.lukesmith.xyz
• SMTP port: 587
• IMAP server: mail.lukesmith.xyz
• IMAP port: 993

In previous versions of emailwiz, you also had to log on with only your username (i.e. luke) rather than your whole email address (i.e. luke@lukesmith.xyz), which caused some confusion. This is no longer the case.

Benefited from this?

I am always glad to hear this script is still making life easy for people! If this script or documentation has saved you some frustration, you can donate to support me at lukesmith.xyz/donate.

Troubleshooting -- Can’t send mail?

• Always check journalctl -xe to see the specific problem.
• Check with your VPS host and ask them to enable mail ports. Some providers disable them by default. It shouldn’t take any time.
• Go to this site to test your TXT records. If your DKIM, SPF or DMARC tests fail you probably copied in the TXT records incorrectly.
• If everything looks good and you can send mail, but it still goes to Gmail or another big provider’s spam directory, your domain (especially if it’s a new one) might be on a public spam list. Check this site to see if it is. Don’t worry if you are: sometimes especially new domains are automatically assumed to be spam temporarily. If you are blacklisted by one of these, look into it and it will explain why and how to remove yourself.
• Check your DNS settings using this site, it’ll report any issues with your MX records
• Ensure that port 25 is open on your server. Vultr for instance blocks this by default, you need to open a support ticket with them to open it. You can’t send mail if 25 is blocked
  • Alternatively you could use a service like Sendgrid as a relay for your outgoing mail. These services usually offer 100 outgoing mails/day for free which should be plenty. This removes the need for opening port 25 and minimizes the risk of getting blacklisted and your mail landing in spam folders. To integrate Sendgrid with Postfix you can refer to this guide.