How to Streamline Email Delivery with Azure SMTP Relay

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Email is an integral communication tool for businesses. But managing email infrastructure to ensure it's fast and effective but still protects against cyber attacks can be daunting. A reliable email delivery solution is necessary to guarantee important messages reach their intended recipients on time.

Azure SMTP Relay is a cloud-based email delivery service that simplifies delivery, boosts reliability, and strengthens security. Azure SMTP Relay offers an economical, scalable, and efficient solution, whether you're sending transactional emails or marketing campaigns.

In this article, we will discuss the benefits of Azure SMTP Relay for email delivery and offer tips and tricks to implement it in your email infrastructure easily.

Azure SMTP Overview

Azure SMTP (Simple Mail Transfer Protocol) is a cloud-based service where employees can securely and reliably send emails from devices and applications without needing an on-premises email server.

Azure SMTP uses the Transport Layer Security (TLS) encryption method to protect email transmissions and also supports authentication methods such as:

  • SMTP authentication
  • Simple Authentication and Security Layer (SALS)
  • Domain-based Message Authentication
  • Reporting
  • Conformance (DMARC)

Azure SMTP is a great fit for businesses that want a reliable and cost-effective way to handle a high volume of daily emails with clients, partners, and employees. Businesses can benefit from its email metrics (delivery rate, bounce rate, and open rate), monitoring feature, and email delivery automation.

Microsoft 365 SMTP Settings

Microsoft 365 SMTP Settings

Microsoft 365 SMTP settings are required in order to send emails from your Microsoft 365 account through an external source. A subset of Azure SMTP, which is an all-encompassing email management solution, is Microsoft 365 SMTP. To prevent spam and make sure your email usage stays within the permitted limits, it's critical to be aware of the email sending restrictions.

The Microsoft 365 SMTP settings that you'll need to configure in your email client or application include:

  • Server Name:
  • Port Number: 587 (recommended) or 25
  • Encryption Method: STARTTLS

By using these settings correctly, you can send emails from your Microsoft 365 account through an external source, such as an application. However, there are certain limitations on the number of emails you can send daily or per minute to avoid spamming. So, to ensure you're aware of these limitations while working with Azure SMTP, review the Microsoft documentation.

The limits, however, are quite generous. For instance, the total receiving limit for emails, regardless of whether you're using Business Basic and Standard or Enterprise F3, is 3,600 every hour. For a single user, the limit is 33% of that, which works out to approximately 1,188 emails per hour.

It's important to note that Microsoft depreciated basic authentication for the Microsoft Office 365 SMTP server. The reason is that through basic authentication, attackers could more easily capture user credentials, which could then be used to access other endpoints or services as well.

This means that applications that only support basic authentication have also been depreciated. Instead, Microsoft business customers will need to move to applications with modern authentication, such as Multi-Factor Authentication (MFA) or Single Sign-On.

In terms of email, this means that different configurations and settings may be needed for tenants on certain versions of Exchange Online. One of the ways this can easily be checked and managed is through the Azure Active Directory Sign-in Report. However, it's important to note that using this service requires a premium license.

Options for impacted protocols are available via Microsoft's basic authentication depreciation documentation.

SMTP Relay Azure Features

Azure SMTP Relay offers a range of features to enhance the email delivery experience for users. Some key benefits include:

Industry-Standard Protocols

Azure SMTP protects your email messages from unauthorized access using industry-standard protocols and encryption. There are many encryptions/protocols that SMTP Relay offers, but Transport Layer Security (TLS) and Secure Sockets Layer (SSL) are the most common and useful.

Managed and Custom Domains

Azure SMTP Relay offers two ways to send email messages:

  • From a pre-provisioned managed domain (
  • Through a custom domain

You can also send emails from your verified domain (e.g., This helps you improve the email deliverability of your businesses, resulting in improved brand identity as well.

Sender Authentication Support

Along with ARC (Authenticated Received Chain) support, Azure SMTP Relay also offers SPF (Sender Policy Framework) and DKIM (Domain Keys Identified Mail) support for both Azure-managed and custom domains. This ensures the email authentication result remains unchanged during transitioning and that the emails are not marked spam or rejected by the recipient's mail servers.

Email Spam Protection and Fraud Detection

Providing email hygiene for all messages is another important feature of Azure SMTP Relay. It also offers powerful Microsoft Defender components that efficiently leverage email protection. The platform enables the existing transport rules for detecting malware, content heuristics, and URL blocking, which helps protect against email spam and fraud.

Email Analytics

Email analytics through Azure Insights is also offered through Azure SMTP Relay. This enables users to track email performance and gain insights into email delivery. To meet GDPR requirements, the platform emits logs at the request level, which contain message ID and recipient information for diagnostic and auditing purposes.

Engagement Tracking

Engagement tracking, including bounce, blocked, open, and click tracking, is supported through Azure SMTP Relay. These metrics help users understand how recipients interact with their email messages and can be used to help improve email engagement rates.

Benefits of Using Azure SMTP for Email Delivery

Benefits of Using Azure SMTP for Email DeliveryBenefits of Using Azure SMTP for Email Delivery

The following are some benefits of using Azure SMTP for email delivery:

Increased Deliverability

Azure SMTP ensures that your email messages make it through to the recipient's inbox through the Azure Email Communication Service, which helps prevent important emails from being marked as spam or ending up in the junk folder. In addition, it also ensures that your emails are protected from phishing attempts and spoofing.

Improved Security

Industry-standard protocols and encryptions like TLS, SALS, DMARC, etc., are utilized by Azure SMTP to help ensure that your email messages are sent securely and are protected from unauthorized access. The platform also supports Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) authentication protocols that prevent unauthorized emails from being sent from your domain. The built-in spam and virus protection feature also adds an extra layer of security.


Designed to be highly scalable, Azure SMTP enables users to handle large volumes of email messages as their needs grow. You can quickly expand your email delivery requirements without worrying about increased infrastructure management, server capacity, or bandwidth limitations.

Customizable Settings

Azure SMTP has a customizable email settings feature to meet your needs. You can configure DNS settings, IP addresses, and email aliases to relay email messages based on different requirements. You can be certain that your email delivery consistently displays your brand image and satisfies your unique business requirements by tailoring your email settings in Azure SMTP. This can increase your email campaigns' deliverability and efficacy and raise consumer engagement and satisfaction.

Centralized Management

Administer multiple domains and email accounts from a single location using Azure SMTP, which aids in simplifying and managing your email infrastructure. This allows easy monitoring of email delivery performance and quick troubleshooting of any issues.


One of the biggest advantages of using Azure SMTP is that you only pay for the resources you use. This makes it more cost-effective than manually setting up and managing your email infrastructure. With Azure SMTP, you can reduce your IT overhead and focus on your core business.

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Best Practices for Using Azure SMTP Relay in Office 365

Azure SMTP Relay in Office 365 Best Practices

An SMTP relay service can be a reliable and convenient option when sending emails from Azure applications like Office 365. However, to ensure optimal performance and to prevent potential issues, it's important to follow best practices for using Azure SMTP relay.

Tips for Optimizing Email Delivery Using Azure SMTP

Here are the best practices to help ensure a smooth and successful integration of Azure SMTP Relay with Office 365:

  1. Obtain the public IP address: Obtain the public (static) IP address from which the device or application will send. Dynamic IP addresses are not allowed. Don't share the IP address with anyone outside of your company, but you can share it with other devices and users within your company.
  2. Check for verification: Check that the domains the application or device will send to have been verified in Microsoft 365 or Office 365. If not, emails could be lost, and you won't be able to track them with the Exchange Online message trace tool.
  3. Select the connector: Go to Mail flow > Connectors in the Exchange admin center. Check the list of connectors set up for your organization. If no connector is listed from your organization's email server to Microsoft 365 or Office 365, create a connector in the Exchange Admin Center (EAC):

For Classic EAC

For New EAC

  1. Open the EAC at and go to Mail flow > Connectors.
  2. Click Add and choose "From your organization's email server to Microsoft 365 or Office 365."
  3. Give the connector a name and choose to verify that the IP address of the sending server and your organization matches.
  4. Add the IP address from Step 1. Leave all other fields with their default values
  5. Select Save.
  1. Open the EAC at and go to Mail flow > Connectors.
  2. Click Add a Connector and choose "Your organization's email server" for the sending server and "Office 365" for the destination server.
  3. Provide a name for the connector and choose to verify that the IP address of the sending server and your organization matches.
  4. Add the IP address from Step 1.
  5. Click Save.
  1. Update DNS: Updating your DNS record on your domain registrar's website is another thing you can do to optimize email delivery. Start by editing your SPF record and including the IP address. The final string should resemble v=spf1 ip4: ~all, considering as your public IP address.
  2. Send test email: Send a test email from your device or application to confirm receipt.

Explanation of Email Authentication Protocols: SPF

DMARC, DKIM, and SPF are three email authentication methods designed to stop spammers, phishers, and other unauthorized parties from sending emails on behalf of a domain they do not control. These measures protect email accounts from being used incorrectly or fraudulently.

What is SPF and How Does it Work?

Sender Policy Framework (SPF) is a way for domains to identify all servers from which they send emails. SPF records contain IP addresses of allowed senders within a domain, similar to how an employee directory lists all employees. Mail servers receiving an email message can check it against this SPF record before forwarding it to its intended recipient's inbox.

What is DKIM and How Does it Work?

DomainKeys Identified Mail (DKIM) allows domain owners to automatically "sign" emails from their domain. A DKIM "signature" is a digital signature that uses cryptography to verify that the email originated from within the domain mathematically; specifically, DKIM utilizes public key cryptography.

What is DMARC and How Does it Work?

Domain-based Message Authentication Reporting and Conformance (DMARC) instructs receiving email servers what to do when certain checks have been made after checking SPF and DKIM for a domain. A domain's DMARC policy can be set in various ways, including:

  • It may instruct mail servers to quarantine emails that do not pass SPF/DKIM verification
  • Reject emails outright
  • Deliver emails as intended.

These policies are stored in DMARC records. DMARC reports provide administrators with the data to adjust their policies accordingly. Furthermore, DMARC records may include instructions for sending reports to domain administrators about which emails are passing and failing these checks.

Monitoring and Troubleshooting with Azure SMTP

Troubleshooting with Azure SMTP

Email delivery is of the utmost importance for any business, and having the appropriate tools to monitor and resolve any issues is necessary. This section will examine how Azure SMTP provides robust monitoring and troubleshooting capabilities that guarantee reliable email delivery.

Overview of Azure SMTP Monitoring Tools and How to Use Them

Azure SMTP monitoring tools help you monitor your SMTP service's performance, detect and troubleshoot issues, and ensure your emails are delivered successfully. Here's an overview of some Azure SMTP monitoring tools and how to use them:

Azure Monitor

As an advanced solution for collecting and analyzing telemetry data from cloud and on-premises environments, Azure Monitor collects information from multiple Azure subscriptions, tenants, and other services hosted on Azure.

This allows you to monitor applications, virtual machines, guest operating systems, databases, networking events, and custom sources. Azure Monitor also enables you to export monitoring data into other systems and integrate with third-party and open-source monitoring tools, as well as ticketing and ITSM applications.

It offers observability by correlating data from multiple sources like metrics, logs, traces, and changes and providing a common set of tools for analyzing and correlating this information.

Azure Application Insights

Application Insights, an extension of Azure Monitor, offers Associate Performance Monitoring (APM) features that proactively monitor and review applications in development, testing, and production. It collects metrics, telemetry, and trace logging data to view application activity comprehensively.

Application Insights offers additional capabilities like Live Metrics, Availability, GitHub/Azure DevOps integration, usage monitoring, and Smart Detection. Distributed Tracing allows end-to-end tracing for execution or transaction, while the Application Map offers a high-level view of application architecture.

Consider consulting the Application Insights deployment planning guide to determine how many resources are required for your deployment planning guide.


As a powerful command-line tool provided by Microsoft, PowerShell allows you to manage and monitor your SMTP service. To use PowerShell to monitor your SMTP service, you need to connect to your SMTP server using PowerShell.

PowerShell is a scripting language that automates system management and builds, tests and deploys solutions. The extensible nature of PowerShell enables it to deploy and manage almost any technology, including Microsoft Azure, Windows, and third-party tools like AWS and VMWare.

It is a versatile, cross-platform task automation solution with a command-line shell, scripting language, and configuration management framework. The shell features a full command-line history, tab completion, and a pipeline for chaining commands.

PowerShell Desired State Configuration (DSC) allows for creating declarative configurations and custom scripts for repeatable deployments and enforcing configuration settings with push or pull models for deployment.

Common Issues With Email Delivery and Troubleshooting Tips

Email delivery failures can be frustrating, especially when sending important messages. Here are three common issues and troubleshooting tips to help you resolve them.

1. Bounces

A bounce happens when an email you send is returned to you because the recipient's inbox is full (soft bounce) or because the email address doesn't exist (hard bounce). To resolve this issue:

  1. Check that you've entered the email address correctly and it's still valid.
  2. If it's a soft bounce, wait and try again later.
  3. Remove the email address from your list if it's a hard bounce.

2. Malware Attack

You may have been under a malware attack if you receive a "Mail Delivery Failure'' notification for messages you didn't send. A virus could use your email account to send spam emails, causing bounces.

To solve this problem, run an antivirus scan on your computer and consider getting email authentication as an anti-spoofing technique.

3. SMTP Issues

A message can be blocked by an anti-spam filter or rejected by the recipient's inbox due to issues with your SMTP server. If the reputation of its sending IP is low or put on a blacklist, your emails will not reach their destination.

To improve delivery rates, consider using a professional SMTP server like Azure SMTP, which uses guaranteed IPs and proper authentication.

By understanding these common issues and taking appropriate measures, you can troubleshoot email delivery problems and ensure your messages reach their intended recipients.


Azure SMTP Conclusion

Using Azure SMTP for email delivery offers a reliable and secure solution with numerous advantages. Users can use Azure's cloud infrastructure to guarantee high deliverability rates while avoiding common email delivery issues. Moreover, its scalability and flexibility in managing email volumes make it ideal for businesses of all sizes.

Implementing Azure SMTP in your email infrastructure is a straightforward process. Start by signing up for an Azure account and selecting the SMTP option from the email settings. Then, configure your email client or application to use the Azure SMTP server when sending emails out. Lastly, monitor delivery and performance with Azure's built-in analytics tools.

By following these steps, you can take advantage of Azure SMTP and ensure a reliable email delivery experience for your organization. If you require assistance setting up or have any queries, consider contacting Amaxra—an established Microsoft Gold Partner with expertise in cloud solutions and IT consulting.

Take the first step towards improving your email infrastructure by contacting Amaxra now.

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