Many businesses manage their email marketing and transactional emails through various platforms. When it comes to Klaviyo, a common question arises: can you integrate an external SMTP service for sending emails? The straightforward answer is that Klaviyo is designed as a complete email service provider (ESP) with its own robust sending infrastructure. This means that for most marketing and transactional emails, Klaviyo handles the actual sending process directly, rather than allowing you to "hook in" your own external SMTP server in the traditional sense.
The platform is built to manage deliverability, compliance, and scale on your behalf. While you might use an external SMTP for other purposes, like sending emails from a custom application or a different system, Klaviyo typically doesn't offer a direct integration point where you can configure it to route its campaigns or flows through your specific external SMTP provider. This approach allows Klaviyo to maintain strict control over its sending reputation and ensure high deliverability rates for its users.
Klaviyo's approach to email sending
Klaviyo's core functionality relies on its internal email sending mechanisms. When you set up your account and connect your sending domain, you're essentially configuring Klaviyo to send emails on your behalf, using its dedicated infrastructure. This involves setting up the necessary DNS records, such as SPF and DKIM, within your domain's DNS settings. These records tell receiving mail servers that Klaviyo is authorized to send email using your domain, which is crucial for email authentication and deliverability.
For transactional emails, which are often time-sensitive and critical, Klaviyo provides dedicated APIs. This is the recommended method for sending emails triggered by specific user actions or system events from your own applications. By using the API, your system sends data to Klaviyo, and then Klaviyo's infrastructure handles the email dispatch, ensuring proper authentication and adherence to deliverability best practices. This ensures that even highly dynamic or automated emails benefit from Klaviyo's optimized sending environment.
The focus is on setting up a branded sending domain within Klaviyo itself. This means that while you control the domain, Klaviyo manages the server-side aspects of sending. This simplifies the process for marketers, as they don't need to worry about the complexities of managing an SMTP server, IP reputation, or dealing with mail transfer agents.
Klaviyo's built-in sending
Klaviyo manages the SMTP servers, IP addresses, and overall sending infrastructure. This provides a hands-off approach to email dispatch, allowing users to focus on content and strategy.
They handle the complexities of email deliverability, including reputation management and compliance with ISP requirements. Users benefit from their optimized sending practices.
Integration with your domain is via DNS records like SPF, DKIM, and DMARC, which authenticate Klaviyo as an authorized sender for your domain.
Why external SMTP integration is often sought
While Klaviyo doesn't support using an external SMTP for its core marketing and flow emails, there are valid reasons why a business might want to consider using a different email sending service for certain types of communications. One primary reason is for high-volume or sensitive transactional emails that are generated by other systems, such as order confirmations, password resets, or shipping notifications.
Another reason could be to maintain a unified sending strategy across an organization, especially if multiple systems send emails and they all leverage a single, dedicated SMTP provider for consistency in branding, authentication, and monitoring. This can be particularly relevant for large enterprises with complex IT infrastructures. Furthermore, some companies prefer the granular control that comes with managing their own SMTP or using a third-party SMTP service directly, especially concerning IP reputation management or specific compliance requirements.
However, it's crucial to understand that if you choose to send transactional emails through a separate SMTP provider (like SMTP.com, Mailgun, or SendGrid), these emails would not be sent through Klaviyo's infrastructure. This means they would not automatically benefit from Klaviyo's tracking, analytics, or segmentation capabilities, unless you explicitly integrate data back into Klaviyo via its API. This separation can lead to fragmented data and a less unified view of customer interactions if not managed carefully.
Alternatives to direct SMTP integration
Since direct external SMTP integration for Klaviyo's primary sending is not an option, you need to consider how to manage transactional emails that originate from other systems while still leveraging Klaviyo's capabilities. The most effective method is to utilize Klaviyo's robust API. This allows your external applications to trigger emails through Klaviyo by sending specific data (like customer profiles and event details) to Klaviyo's API endpoints. Klaviyo then uses this data to send the email from its own servers, ensuring proper branding, authentication, and tracking within the platform.
Another powerful alternative for integrating external systems and data with Klaviyo is through webhooks. Webhooks allow real-time communication between your applications and Klaviyo. For instance, if an event occurs in your e-commerce platform (like a new order), a webhook can instantly send that data to Klaviyo, triggering a specific flow or email in response. This ensures that even if emails are technically sent from Klaviyo's infrastructure, they are responsive to actions happening in your external systems.
Integration platforms, often referred to as iPaaS (Integration Platform as a Service) solutions, also provide a bridge between Klaviyo and various other applications. Tools like Zoho Flow or Integrately can automate data flow between your systems and Klaviyo, enabling complex workflows without requiring extensive custom coding. These platforms can facilitate sending events or profile updates to Klaviyo, which then triggers email sending within Klaviyo's environment. This provides a flexible way to achieve integration goals without needing to directly manipulate SMTP settings.
For specific use cases where you absolutely must send transactional emails from a separate SMTP provider, you will manage those emails entirely outside of Klaviyo. This is common for critical system notifications that require very high delivery guarantees or strict control over the sending environment. In such cases, you would configure the SMTP settings within your application or server, as detailed in guides for managing transactional emails through your own SMTP server. However, remember that these emails would not be visible or tracked within your Klaviyo account.
Domain authentication and deliverability
Regardless of whether you use Klaviyo's internal sending or an external SMTP for transactional emails, robust domain authentication is paramount for deliverability. This involves correctly configuring SPF, DKIM, and DMARC records for your sending domain. These DNS records serve as critical signals to receiving mail servers, verifying that the emails coming from your domain are legitimate and authorized. Without proper authentication, your emails are highly likely to land in spam folders or be outright rejected by mailbox providers.
When using Klaviyo, it provides specific instructions for setting up these records, which typically involves adding CNAME records (for DKIM and branded sending) and TXT records (for SPF and DMARC) in your DNS provider. It is essential to ensure that these records are correctly published and that there are no conflicts, especially if you're using multiple email sending services or a subdomain for email sending. Misconfigurations can lead to significant deliverability issues, impacting your sender reputation and inbox placement.
Regularly checking your authentication setup is a crucial best practice. Tools that allow you to troubleshoot DMARC, SPF, and DKIM setup issues can help you identify and resolve problems quickly. Proper alignment of SPF and DKIM with your DMARC policy is essential for achieving the highest level of email authentication. This is particularly important with new sender requirements from major mailbox providers that emphasize strong authentication for all senders.
Klaviyo's sending
Setup: Klaviyo handles the sending infrastructure. You connect your domain via DNS records.
Deliverability: Optimized by Klaviyo's team. Benefits from their shared or dedicated IP pools and reputation management.
Tracking: Full visibility into opens, clicks, and conversions directly within Klaviyo's dashboard.
Best for: Marketing campaigns, automated flows, and primary transactional emails integrated via Klaviyo's API.
External SMTP sending
Setup: You manage the SMTP server, configuration, and IP reputation.
Deliverability: Your responsibility. Requires vigilant monitoring to avoid blocklists or low inbox placement.
Tracking: Requires separate logging and reporting mechanisms from your SMTP provider. Data not in Klaviyo.
Best for: System notifications, custom application emails, or very specific compliance needs outside Klaviyo.
Data management and deliverability implications
Integrating external systems with an ESP like Klaviyo often involves careful consideration of data flow and how it impacts your overall email strategy. If you choose to send certain transactional emails through an external SMTP provider, you must account for the data separation. Information about these emails (opens, clicks, bounces) will reside with your external SMTP provider, not automatically within Klaviyo. This can create challenges for a unified view of customer engagement and for segmenting users based on all their email interactions.
Another critical consideration is deliverability. While Klaviyo manages its sending reputation meticulously, when you use an external SMTP, the responsibility for maintaining a healthy sender reputation falls on you. This means proactive monitoring for email blacklists (or blocklists), handling bounces, and ensuring consistent authentication are vital. Any issues with your external SMTP could negatively impact the deliverability of those specific emails.
Ultimately, the decision to use Klaviyo's internal sending versus a separate SMTP provider for specific email types hinges on your business's unique needs, technical capabilities, and desire for control. For most marketing and automated flows, Klaviyo's native sending capabilities are more than sufficient and highly recommended. For very specific transactional email needs from external applications, using Klaviyo's API to send via their infrastructure or a separate dedicated transactional email service is the way to go.
Views from the trenches
Best practices
Always prioritize setting up and verifying your branded sending domain within Klaviyo for optimal performance and deliverability.
Utilize Klaviyo's APIs for sending transactional emails from external systems to leverage their infrastructure and analytics.
Ensure all necessary DNS records (SPF, DKIM, DMARC) are correctly configured for your sending domains on all platforms.
Common pitfalls
Expecting Klaviyo to act as a pass-through SMTP for external email sending, which it is not designed to do.
Failing to set up proper authentication (SPF, DKIM, DMARC) when using multiple sending services.
Not integrating transactional email data back into Klaviyo, leading to incomplete customer profiles.
Expert tips
Use a subdomain for transactional emails if sending them from a separate SMTP to isolate reputation risks from your main marketing domain.
Regularly monitor your domain's health and deliverability metrics across all sending platforms.
Consider using an iPaaS solution to automate data synchronization between Klaviyo and other tools for a unified customer view.
Marketer view
Marketer from Email Geeks says that if direct external SMTP integration isn't supported, alternative transactional email providers like Mailgun, SendGrid, or Mandrill should be considered.
2024-02-02 - Email Geeks
Marketer view
Marketer from Email Geeks says that Klaviyo does not offer a direct way to hook into your own external SMTP server.
2024-02-02 - Email Geeks
Navigating your email sending strategy with Klaviyo
While Klaviyo doesn't offer a direct SMTP integration for its core email sending, its robust API and webhook capabilities provide flexible alternatives for managing transactional emails and data from external systems. By understanding Klaviyo's design as a comprehensive ESP, you can leverage its strengths for marketing and automated communications while strategically addressing other email sending needs through its API or a separate transactional email provider. Ensuring proper domain authentication across all sending platforms is key to maintaining strong deliverability and avoiding blocklists, regardless of your chosen strategy.
Klaviyo handles the sending infrastructure. You connect your domain via DNS records. 
