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Resolving Email Delivery Issues Between Office 365 and Gmail: A Case Study

In today’s digital world, email communication has become a cornerstone for businesses worldwide, facilitating seamless interaction within organizations and with external partners. However, this crucial tool can sometimes encounter delivery issues, causing significant disruption in communication. A notable increase in such incidents has been observed recently, largely attributed to changes Gmail has implemented to enhance its spam filtering techniques. These adjustments, although aimed at reducing unwanted emails, have inadvertently affected legitimate email traffic from other services, such as Office 365. This blog article delves into a challenging situation where a client faced difficulties in delivering emails from Office 365 to Gmail. With both Office 365 and Gmail support teams initially unable to pinpoint the problem, leading to weeks of emails being mistakenly flagged as spam, the resolution required a detailed and systematic approach. Here’s how we tackled the issue and restored seamless email communication.

The Initial Problem

The client, who had recently transitioned to Office 365 for their email services, reported that their emails to Gmail addresses were consistently being marked as spam. This issue was perplexing and significantly hindered their ability to communicate with stakeholders using Gmail. Upon contacting support teams from both Office 365 and Gmail, each pointed fingers at the other, leaving the client in a challenging position without a clear path forward.

The Resolution Process

After a thorough analysis of the situation, we identified a series of steps that eventually led to a resolution. Here’s a breakdown of the measures we implemented:

1. Standardizing the Domain Name in Office 365

The first discrepancy we noticed was in the representation of the domain name in Office 365. The domain had been entered using uppercase letters, contrary to the standard practice of using lowercase. We corrected this by adding the primary domain to Office 365 using lowercase letters. This seemingly minor adjustment was the first step in aligning with standard email configuration practices.

2. Updating DNS Entries

Next, we focused on the DNS (Domain Name System) settings. Proper DNS configuration is crucial for directing email traffic and authenticating a domain. We incorporated the necessary MX (Mail Exchange), CNAME (Canonical Name), and TXT (SPF) records provided by Office 365 into the client’s DNS provider. These entries are essential for routing emails correctly and for email authentication processes.

3. Implementing DKIM in Office 365

DomainKeys Identified Mail (DKIM) adds an extra layer of security by attaching a digital signature to outgoing emails. This signature helps verify that the emails are genuinely from the domain they claim to be from, enhancing trust and email deliverability. We set up DKIM in Office 365 for the client, ensuring that their emails had this important verification tool.

4. Implementing DMARC for Additional Security

Domain-based Message Authentication, Reporting, and Conformance (DMARC) is a protocol that uses SPF and DKIM to determine the authenticity of an email. It also instructs receiving servers on how to handle emails that fail these checks, providing another layer of protection against email spoofing and phishing attacks. We added a DMARC record to the client’s DNS settings, configuring it to inform us of any issues while preventing unauthorized use of the domain.

The Outcome

After implementing these steps, we observed a significant improvement in email deliverability from Office 365 to Gmail. Emails were no longer being marked as spam, and the client was able to resume normal communication with their Gmail-using contacts. This case highlights the importance of proper email configuration and the effectiveness of a methodical approach to troubleshooting.


Dealing with email deliverability issues can be a frustrating experience, especially when it seems like you’re getting the runaround from support teams. However, by understanding the underlying technologies and protocols, such as SPF, DKIM, and DMARC, and ensuring that your domain and email settings are correctly configured, most issues can be resolved. This case study serves as a reminder of the critical role of technical diligence and the need for clear communication between service providers and clients to overcome challenges in the digital communication landscape.


Based in Burbank, California, Vimware is an Amazon AWS partner offering specialized IT strategy and software development consulting. With a focus on empowering small to midsize businesses, our expertise in building apps, websites, SAAS, APIs, and DevOps ensures your organization excels in the digital arena. Looking for more details or services? Contact us—we’re dedicated to providing the support you need!


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