Simple Mail Transfer Protocol (SMTP) is a standard protocol used to send, receive, and relay email messages between servers, email clients, and other email-related applications. Installing and configuring an SMTP server allows you to send outbound emails from your own domain rather than relying on an external email provider.
Key benefits of running your own SMTP server include:
- More control over email delivery and security
- Ability to send automated emails from web apps
- No per-email costs associated with external email services
- Custom domain for sender addresses rather than @gmail.com etc
Common SMTP server software options:
- Microsoft Exchange Server
Considerations before installing an SMTP server
There are a few key considerations before deciding to install and run your own SMTP server:
- Requires a dedicated IP address with good reputation
- Can be complex to properly secure and maintain
- You become responsible for delivery, spam filtering, virus scanning etc
- Some ISPs block outbound SMTP traffic on certain ports
Overall, running your own SMTP server gives you flexibility and control over email, at the cost of additional server overhead. Leveraging a third-party ESP may be easier for small organizations.
Step-by-Step Guide to Installing an SMTP Server
Follow this step-by-step guide to properly install, configure, and test a fully-functional SMTP server on your infrastructure.
1. Choose your SMTP server software
The first step is to decide which SMTP software you want to use. The most popular free options are Sendmail and Postfix. For Windows administrators, Microsoft Exchange Server or hMailServer may be easier to work with.
For this guide, we’ll use Postfix on an Ubuntu 20.04 Linux server.
2. Install Postfix SMTP software
Log into your Ubuntu server via SSH and run the following commands:
sudo apt update
sudo apt install postfix
Select “Internet Site” during the postfix configuration prompts.
3. Configure SMTP domains and networks
Open /etc/postfix/main.cf in a text editor with sudo privileges:
sudo nano /etc/postfix/main.cf
Update the mydestination, myhostname, mydomain, and mynetworks parameters with your settings:
mydestination = $myhostname, localhost.$mydomain
myhostname = mail.yourdomain.com
mydomain = yourdomain.com
mynetworks = 192.168.1.0/24 127.0.0.0/8 [::1]/128
Save and exit the file when finished.
4. Configure relay host IP access
Still within main.cf, find the relayhost directive and update it to only allow your outbound IP address to relay mail through your SMTP server:
relayhost = [your.ip.address]
This enhances security by restricting open relay access.
5. Restart or reload Postfix
Apply the configuration changes by restarting postfix:
sudo systemctl restart postfix
Check the status with systemctl status postfix to confirm a successful restart.
6. Open required ports
On most networks, you’ll need to open the following ports on your firewall to allow SMTP traffic:
- 25 – SMTP
- 465 – SMTPS (implicit TLS)
- 587 – Submission (explicit TLS)
Open these ports to client subnets and update your SMTP server’s security groups if on the public cloud.
7. Test sending email
The basic Postfix SMTP configuration is now complete. Let’s confirm it works by sending a test email either locally or from another server.
You may need to install mailutils first:
sudo apt install mailutils
Then send a test email with mail command:
echo “This is a test email from the SMTP server” | mail -s “SMTP test” [email protected]
Check if the email was successfully delivered to the destination inbox. Troubleshoot configuration issues as necessary.
8. Secure your SMTP server
With basic functionality confirmed, lock down security on your new Postfix by:
- Enforcing TLS encryption
- Requiring authentication to send mail
- Configuring spam filters like SpamAssassin
- Setting up SPF and DKIM
- Limiting accounts that can relay mail
Refer to Postfix documentation for detailed direction on production hardening.
Congratulations! You now have a fully functioning standards-compliant SMTP server for sending email from your hosts and applications.
Key Takeaways for Installing SMTP Server
To recap, the key steps covered for installing and configuring a Postfix SMTP email server on Ubuntu Linux were:
- Install Postfix mail server software with apt
- Configure SMTP domains, hostname, and networks
- Set relay restrictions for security
- Restart or reload the Postfix service
- Open necessary SMTP ports on firewalls
- Test sending email for confirmation
- Harden security before production use
Following this best practice process allows you to deploy a flexible SMTP server to handle critical outbound email deliverability from your own infrastructure.
Conclusion and Next Steps
Setting up your own SMTP server provides increased delivery control and customization for email sent from web apps and other services. But running a secure, reliable mail server takes time and expertise.
Evaluate whether offloading email deliverability to a trusted third-party ESP is a better fit, especially when first getting started. Options like Mailgun, SendGrid, Amazon SES take care of the operational overhead for your mailing infrastructure.
If deploying your own server, be sure to engineer sufficient redundancy, monitor performance, establish backup plans, and keep up with SMTP best practices. Email is a vital business function for reaching customers and users. Both your chosen technology and configurations should fit the critical nature of this communication channel.
Frequently Asked Questions about Installing SMTP Servers
- What are the benefits of self-hosting an SMTP server?
Owning your mail server gives you full control over deliverability, security policies, IP reputation, and customization. You can also save money by avoiding usage costs of external ESPs.
- What email protocols does an SMTP server support?
SMTP focuses specifically on transmission of email messages. Related protocols like IMAP and POP3 handle accessing inboxes for retrieval of messages.
- Is SMTP the same as sending email?
Essentially yes – SMTP dictates the content, commands, and process for getting email routed from senders to recipient inboxes.
- Can I use Gmail or Outlook as an SMTP server?
Major email providers may offer limited SMTP access, but typically block mass sending due to spam policies. They also require authentication and TLS for security compliance.
- What’s the difference between SMTP vs SES?
Amazon SES is cloud-based email sending service. It handles SMTP complexity behind the scenes while exposing clean APIs/SDKs for programmatic bulk email delivery.
- What should an SMTP server’s IP address be?
A dedicated static IP address with positive reputation helps ensure reliable email delivery. Some ISPs frequently cycle consumer dynamic IPs causing deliverability issues.
- How do I choose which SMTP server software to use?
Evaluate platforms like Sendmail, Postfix, or Exchange Server based on your skillset and technical requirements. Open source options like Postfix offer more customization for advanced administrators.
- Can I use SMTP to receive email too?
No – SMTP is designed for outbound message sending rather than storage and retrieval of messages. Use protocols like POP3 or IMAP for fetching inboxes.
- Is Sendmail better than Postfix for SMTP?
Sendmail historically came first, but Postfix has emerged as a popular open-source alternative for Linux mail servers. Performance and security between modern versions are comparable.
- What tools should I use to monitor my SMTP server?
Solutions like Mail-Tester, MXToolbox, and 250ok can validate DNS records, test connectivity, confirm security policies, and check email deliverability in real-time.