What is custom SMTP?

A custom SMTP server allows you to send emails using your own domain name and IP address instead of your email provider’s domain name and servers. This gives you more control, security, and deliverability when sending emails.

What is custom SMTP?

Benefits of a custom SMTP server

Here are some of the main benefits of using a custom SMTP server:

  • Use your own domain name – Emails will come from your domain instead of your provider’s domain (e.g. @yourdomain.com instead of @gmail.com)
  • Improve deliverability – Custom SMTP servers have better deliverability and avoid issues caused by shared IP blocks
  • Enhanced analytics – You can track opens, clicks, unsubscribes etc with more accuracy
  • Increased security – Custom SMTP servers give you more control over security and authentication protocols
  • Avoid throttling limits – Shared email providers often throttle limits, custom SMTP servers have higher sending limits

How does a custom SMTP server work?

A custom SMTP server works by integrating with your email provider or software via SMTP. Here is the basic process:

  1. Email is created and sent by your email tool/provider as usual
  2. Instead of using your provider’s SMTP servers, the email is routed to your custom SMTP server
  3. The custom SMTP server sends the email via your own IP address using SMTP protocol
  4. Email arrives in the recipient’s inbox from your domain name, not your provider’s

So you still use your regular email provider or software, but outgoing emails are handled by your own custom SMTP server instead of your provider’s servers.

Setting up a custom SMTP server

There are a few different ways to set up a custom SMTP server:

  • SMTP API – Many email providers like Mailgun, Sendgrid, Sparkpost provide SMTP APIs to send via your domain
  • Self-hosted SMTP – Install SMTP server software like Postfix, Sendmail. Requires hosting/managing your own server
  • Shared SMTP Services – Services like Amazon SES, Mailjet, Mailgun provide shared custom SMTP servers
  • MTA server host – Specialist SMTP hosting services with easy setup like Socketlabs, Dyn, Elastic Email

The easiest options are typically using a SMTP API or service. Self-hosted and MTA hosting require more technical expertise.

Key things to look for in a custom SMTP provider

If using a shared SMTP service, here are key features to look for:

  • Delivery speed – Fast sending and delivery times
  • Uptime & Reliability – High server uptime and reliability
  • Scalability- Ability to scale sending capacity on demand
  • Security- Encryption protocols, authentication, cybersecurity practices
  • Reputation Monitoring- Monitor IP and domain reputation, blacklist monitoring
  • Analytics & Reporting- Track email metrics like opens, clicks, unsubscribes
  • Inbox Placement- Tools to improve inboxing and avoid spam folders
  • Support- Technical support in case issues occur

Custom SMTP use cases

Common use cases for custom SMTP servers include:

  • Sending transactional emails – Order confirmations, password reset emails, notifications
  • Sending marketing campaigns – Newsletters, promotions, email campaigns
  • Improving inbox placement – Avoid spam folders, improve engagement
  • Building or protecting sender reputation – Establish good sending reputation and avoid issues with shared IPs
  • Adding tracking and analytics – Track opens, clicks, unsubscribes at the domain level

Summary of key benefits

To summarize, the key benefits of using a custom SMTP server are:

  • Send from your own domain name instead of your provider’s domain
  • Improve deliverability through dedicated IP addresses and reputation
  • Enable better email tracking, analytics and inbox placement
  • Avoid throttling and sending limits imposed by shared email providers
  • Increase security, reliability and scalability of your email infrastructure

So in short – more control, security and better deliverability!

Key Takeaways

  • Use your own domain – Send from @yourdomain instead of @gmail or other providers
  • Higher deliverability – Dedicated IP addresses avoid issues with shared email IPs
  • Better analytics – Track email metrics like opens, clicks more accurately
  • Increased control – Custom SMTP servers give you more control over email infrastructure
  • Avoid throttling limits – Shared email providers often throttle sending limits


Setting up a custom SMTP server allows you to fully control and manage your email sending infrastructure for maximize deliverability while using your own domain name. While easy SMTP API integrations work for most use cases, businesses sending large volumes of email should consider a dedicated custom SMTP server service or self-hosted option to scale email delivery and analytics capabilities. By improving deliverability rates, security, providing better analytics and avoiding throttling restrictions, custom SMTP servers are a smart investment for any business relying on email marketing and communications.

Frequently Asked Questions

  1. What is the difference between SMTP and custom SMTP?
    SMTP is the protocol used for sending emails globally. Custom SMTP means using your own SMTP server instead of relying solely on your email provider’s SMTP servers.

  2. What are the advantages of a custom SMTP server?
    The main advantages are improved deliverability and inbox placement, increased sending limits, better security, using your own domain instead of your provider’s domain, and more accurate email analytics and tracking.

  3. Does custom SMTP integrate with my email provider?
    Yes, custom SMTP works by integrating with your existing email provider or software via the SMTP protocol. Emails are sent from your provider to your custom SMTP server instead of your provider’s servers.

  4. Do I still need an email provider if I use custom SMTP?
    Yes, you still need an email provider or email marketing platform. Custom SMTP serves as an add-on layer to improve your email sending capabilities.

  5. What are some options for setting up a custom SMTP server?
    Top options are using SMTP APIs from providers like Sendgrid, using shared SMTP server services like Amazon SES or Mailgun, installing your own self-hosted SMTP server, or using an SMTP hosting provider.

  6. How much does a custom SMTP server cost?
    Costs vary widely depending on whether you use an SMTP API, shared service, or dedicated SMTP hosting. Shared services start around $10/month, going up to $1000+/month for dedicated SMTP hosting at scale.

  7. What should I look for in a custom SMTP provider?
    Key features to look for include deliverability rate, server uptime and reliability, ability to scale capacity on demand, security features like encryption and authentication, inbox placement tools, and technical support options.

  8. Will a custom SMTP server help emails get delivered?
    Yes, dedicated IP addresses and closely monitoring reputation helps custom SMTP servers achieve higher deliverability and inbox rates compared to shared consumer email platforms.

  9. Can custom SMTP servers improve email security?
    Yes, most custom SMTP providers offer robust security features like encrypted protocols, login authentication, whitelisting and other tools to enhance email security.

  10. What are some best practices when sending emails?
    Best practices include properly setting SPF and DKIM records, monitoring your sending reputation, focusing on relevant quality content in your emails, and carefully reviewing reports from your custom SMTP provider to maximize email reach and engagement.

  11. Are there downsides to using a custom SMTP server?
    The main downsides are increased complexity and the need to carefully track deliverability and other metrics reported by your custom SMTP provider. For advanced users sending high email volumes, the benefits generally outweigh these costs.

  12. Should I use custom SMTP for sending marketing emails?
    For companies relying on email marketing campaigns, custom SMTP is highly recommended to improve deliverability, avoid throttling from consumer email platforms, gain more insights from tracking and analytics, and establish your own domain reputation.

  13. Can custom SMTP servers be used for sales outreach?
    Yes, custom SMTP servers provide benefits for sales teams doing cold outreach such as professional domain names on outreach emails, improved inbox placement and using tracking to gauge engagement.

  14. Is it difficult to switch over to a custom SMTP server?
    Switching is relatively easy as long as you choose a reputable custom SMTP provider that offers clear documentation and support. Most have integrations that work seamlessly with all major email service providers.

Leave a Comment