How to fix DKIM body hash did not verify errors on Outlook.com and prevent emails from going to spam?

The 'DKIM body hash did not verify' error on Outlook.com, often leading to emails being sent to spam, primarily arises from the email's content being altered after it has been digitally signed by DKIM but before it reaches the recipient's inbox. These modifications can be subtle, such as changes to whitespace, line endings, or the introduction of non-ASCII characters, and are frequently introduced by intermediary services like email forwarding, anti-spam gateways, security filters, or even internal systems adding disclaimers or archiving. Outlook.com is particularly strict in enforcing RFC compliance, making these issues more apparent. A critical solution involves configuring DKIM canonicalization to 'relaxed/relaxed' for both the header and body, which makes the signature more robust against minor, legitimate alterations during transit. Senders should meticulously audit their email flow, compare raw email versions, and work closely with their Email Service Providers to ensure proper DKIM record publication and signing practices. If deliverability issues persist after addressing DKIM, attention should shift to audience engagement and overall sender reputation.

When Outlook.com reports a 'DKIM body hash did not verify' error, leading to emails potentially landing in spam, the fundamental problem is that the email's content has been modified after its digital signature was applied by the sender. These alterations, often subtle and unintentional, can be introduced by various intermediary systems-such as email forwarding services, anti-spam filters, or security gateways-or even by internal infrastructure components like disclaimer adding services or archiving solutions, before the email leaves the sender's network. The most effective preventative measure is to configure DKIM to use 'relaxed' canonicalization for both the header and body, making the signature resilient to minor, legitimate formatting adjustments during transmission. Resolving this requires a thorough audit of the entire email flow, comparing the raw email as sent versus as received by Outlook.com, and working closely with your Email Service Provider to ensure proper DKIM implementation and signing practices.

The 'DKIM body hash did not verify' error, commonly observed on Outlook.com and often resulting in emails being marked as spam, fundamentally indicates that the email's content was altered after the DKIM signature was applied. This frequently occurs when the sending Mail Transfer Agent (MTA) or other services modify the message body, even subtly, by adding elements like footers, removing whitespace, or changing line endings. These post-signature changes invalidate the original DKIM hash, leading to verification failure, particularly given Outlook.com's stringent RFC compliance. To resolve this, email senders must ensure their systems do not alter email content after signing, and a common recommendation is to utilize 'relaxed/relaxed' DKIM canonicalization settings to better tolerate minor modifications. If DKIM issues are resolved but emails continue to be flagged as spam, broader deliverability factors such as audience engagement and sender reputation also warrant investigation.

To address 'DKIM body hash did not verify' errors on Outlook.com and prevent emails from landing in spam, the critical step is to ensure that the email's content remains unchanged after its DKIM signature has been applied. These verification failures frequently stem from subtle modifications introduced by various points in the mail flow, such as anti-spam gateways, forwarding services, or even improper mail flow rules within a Microsoft 365 environment. A highly recommended solution is to configure DKIM with 'relaxed' canonicalization for both the header and body, as this setting significantly enhances the signature's resilience to minor, legitimate alterations during transmission. Additionally, it is essential to verify that your DKIM records are correctly published in DNS and that your sending server accurately applies the signature in accordance with your domain's established policy. Regularly monitoring DKIM failure rates using tools like Google Postmaster Tools can help identify systematic problems that require deeper investigation into your email signing process and overall email delivery chain.