Summary
Hosting an MTA on Microsoft Azure presents numerous challenges, making it generally not recommended without careful consideration. Experts and marketers highlight concerns around IP reputation, with Azure-provided IPs often perceived as blockworthy due to shared pools and lack of warm-up. Azure does not directly offer SMTP relay services but provides alternatives like Azure Communication Services, though these require configuration and may not be as reliable as dedicated ESPs. Companies may face difficulties with port 25 access, especially smaller ones, and configuring Network Security Groups (NSGs) adds complexity. While Azure supports BYOIP, it requires active management. Dedicated ESPs like SendGrid and Mailjet, available on the Azure Marketplace, are frequently recommended for their ease of integration, scalability, and more reliable deliverability, despite potential costs.
Key findings
- IP Reputation Issues: Azure-provided IPs often suffer from poor reputation, leading to deliverability problems.
- No Direct SMTP Relay Service: Azure doesn't offer a direct SMTP relay service, pushing users toward alternatives.
- Complexity with NSGs: Configuring Network Security Groups for SMTP traffic is complex and adds administrative overhead.
- Dedicated ESPs Preferred: Using dedicated ESPs like SendGrid and Mailjet, which integrate well with Azure, is commonly recommended for better deliverability and ease of use.
- BYOIP Support: Azure supports Bring Your Own IP, but it requires active management and warm-up.
- Azure Communication Services: Azure Communication Services provides a potentially cheaper email sending solution but may require extensive configuration.
- Company Size Matters: Larger companies have better negotiating power with cloud providers regarding port 25 access and other service aspects.
Key considerations
- Assess Deliverability Needs: Carefully evaluate the importance of email deliverability and the potential impact of using shared IPs.
- Consider Alternatives: Thoroughly research and compare alternative email sending solutions, including dedicated ESPs and Azure Communication Services.
- Manage IP Reputation: If using Azure IPs or BYOIP, implement a comprehensive IP warm-up and reputation management strategy.
- Evaluate Costs: Compare the costs of self-hosting an MTA on Azure, using Azure Communication Services, and using a dedicated ESP.
- Plan for Configuration Complexity: Be prepared to manage complex configurations, particularly regarding Network Security Groups and other Azure services.
- Factor in Company Size: Consider the company's size and negotiating power when choosing an email sending solution and dealing with cloud providers.
- Monitor Performance: Continuously monitor email sending performance and deliverability metrics to identify and address potential issues proactively.
What email marketers say
10 marketer opinions
Hosting an MTA on Microsoft Azure presents several challenges. While Azure provides services like Azure Communication Services and supports BYOIP (Bring Your Own IP), users often face issues with IP reputation, port 25 blocking, and complex configuration. Many recommend using dedicated email service providers (ESPs) like SendGrid or Mailjet, which integrate well with Azure and offer more reliable deliverability. Azure Communication Services is a cheaper solution, but it may not be as reliable. Running an on-prem MTA on Azure can also be problematic, with Microsoft sometimes blocking its own IP ranges.
Key opinions
- Deliverability Challenges: Maintaining good IP reputation and avoiding port 25 blocking are significant hurdles when hosting an MTA on Azure.
- Dedicated ESPs Recommended: Integrating with dedicated ESPs like SendGrid and Mailjet is generally preferred over self-hosting due to ease of use and better deliverability.
- Azure Communication Services as Alternative: Azure Communication Services provides a cheaper alternative for sending emails but requires configuration.
- BYOIP Support: Azure supports Bring Your Own IP (BYOIP), which can help with reputation management, but it still requires effort to maintain.
- On-Prem MTA Issues: Running on-prem MTAs on Azure VMs can lead to issues with Microsoft blocking its own IP ranges.
Key considerations
- IP Reputation: Carefully manage and monitor IP reputation to ensure high deliverability rates.
- Port 25 Blocking: Be aware of potential port 25 restrictions and configure accordingly.
- Integration Complexity: Understand the complexity of integrating an MTA with Azure services versus using a dedicated ESP.
- Cost: Evaluate the cost-effectiveness of self-hosting an MTA versus using a paid ESP or Azure Communication Services.
- Configuration: Properly configure Azure services and network settings to allow SMTP traffic.
Marketer view
Email marketer from Email Geeks shares that Azure now supports BYOIP (Bring Your Own IP).
20 Feb 2023 - Email Geeks
Marketer view
Email marketer from ServerFault suggests using a dedicated email delivery service is more suitable as Azure isn't suited for this as it's likely to have issues regarding IP reputation.
30 Sep 2022 - ServerFault
What the experts say
4 expert opinions
Experts generally express concerns about using Microsoft Azure as a platform to host an MTA. Key issues include the potential for Azure IPs to be perceived as blockworthy due to shared IP pools and lack of warm-up, leading to deliverability problems. The size of the company also influences the ability to negotiate for better port 25 access. Furthermore, cloud providers like Azure often struggle with maintaining the IP reputation necessary for reliable email delivery.
Key opinions
- IP Reputation Concerns: Azure-provided IPs may have poor reputation, leading to deliverability issues.
- Blockworthy Perception: Using Azure IPs for MTAs can lead to emails being perceived as spam or blocked.
- Negotiating Power: Larger companies have more leverage to negotiate port 25 access with cloud providers.
- Cloud Provider Challenges: Cloud providers often struggle to maintain good IP reputation for email sending.
- Shared IP Pools: Shared IP pools in Azure can lead to deliverability issues due to the actions of other users.
Key considerations
- Alternative MTAs: Consider alternative cloud MTA options like SocketLabs, Sendgrid, SES, and SparkPost.
- IP Warm-up: Properly warm up IPs if using Azure's services for email sending.
- Company Size: Assess the company's size and negotiating power when dealing with cloud providers for email services.
- Reputation Management: Implement robust reputation management strategies to ensure email deliverability.
- Port 25 Access: Understand the limitations and potential challenges with port 25 access on Azure.
Expert view
Expert from Email Geeks shares concerns about using Azure IPs for MTAs, suggesting they might be perceived as blockworthy. He suggests exploring other cloud MTA options like SocketLabs, Sendgrid, SES, and SparkPost.
12 Mar 2025 - Email Geeks
Expert view
Expert from Word to the Wise explains that cloud providers such as Azure frequently have issues with maintaining the reputation of IP addresses used for sending email, potentially affecting email deliverability for users hosting MTAs there.
7 Feb 2024 - Word to the Wise
What the documentation says
4 technical articles
Microsoft Azure documentation suggests that Azure does not directly offer SMTP relay services. Instead, it provides alternatives like Azure Communication Services for sending emails. Azure Communication Services includes email capabilities and can serve as an MTA alternative. Correct configuration of Network Security Groups (NSGs) is crucial for allowing SMTP traffic, but it can be complex. Additionally, SendGrid is available on Azure Marketplace, providing a scalable and reliable email sending solution.
Key findings
- No Direct SMTP Relay: Azure does not directly provide SMTP relay services.
- Azure Communication Services: Azure Communication Services offers email sending and receiving capabilities as an MTA alternative.
- NSG Configuration Complexity: Correctly configuring Network Security Groups (NSGs) for SMTP traffic is complex and adds overhead.
- SendGrid Availability: SendGrid is available on Azure Marketplace, providing a scalable email solution.
Key considerations
- Alternative Solutions: Consider using Azure Communication Services or SendGrid as alternatives to a traditional MTA.
- NSG Management: Carefully manage and configure Network Security Groups (NSGs) to allow SMTP traffic while maintaining security.
- Scalability: Evaluate the scalability needs and whether SendGrid or Azure Communication Services can meet those requirements.
- Complexity: Assess the complexity of managing NSGs and integrating different services for email sending.
Technical article
Documentation from Microsoft Azure Documentation explains that configuring Network Security Groups (NSGs) correctly is crucial for allowing SMTP traffic, but it can be complex to manage and maintain, adding overhead to running an MTA on Azure.
7 Feb 2023 - Microsoft Azure Documentation
Technical article
Documentation from Azure Marketplace explains that SendGrid is available on Azure Marketplace, which allows Azure users to easily deploy and use SendGrid's email sending services, providing a scalable and reliable solution for sending emails.
26 Mar 2022 - Azure Marketplace
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