Does the X-Mailer header impact email deliverability in Zoho Campaigns?

Key findings

• Visibility: The "Using Zoho Campaigns" text is a display feature by Google, triggered by the X-Mailer header, which indicates the sending platform.
• Deliverability impact: The X-Mailer header itself typically does not negatively affect email deliverability, provided your authentication records like SPF, DKIM, and DMARC are correctly configured. For more on this, consider our guide on a simple guide to DMARC, SPF, and DKIM.
• ESPs and headers: Email Service Providers (ESPs) like Zoho Campaigns commonly add X-Mailer headers as part of their standard email metadata.
• Control: Whether you can remove or modify this header depends on the specific settings and flexibility offered by Zoho Campaigns. Many ESPs do not allow users to alter standard headers.

Key considerations

• Focus on fundamentals: Instead of worrying about the X-Mailer header, concentrate on established email deliverability best practices. Zoho themselves recommend focusing on authentication protocols and optimizing content, as detailed in their email deliverability guide.
• Reputation: Maintain a strong sender reputation through consistent sending, low bounce rates, and high engagement to ensure optimal inbox placement. Explore how your email tool affects your email deliverability more broadly.
• User perception: While the "Using Zoho Campaigns" tag is present, most recipients are unlikely to be concerned by it, as long as the email is relevant and legitimate.

Key opinions

• No significant impact: Most marketers haven't observed any data suggesting that the X-Mailer header causes deliverability problems.
• Google's behavior: It's understood that Google (and potentially other email clients) will often display the "Using..." text if an X-Mailer header is present.
• Focus on core elements: The critical elements for deliverability are sender authentication, content relevance, and list hygiene, not minor header details. This aligns with advice on overall email deliverability issues.
• Branding vs. technical: While some might prefer to remove it for aesthetic or branding reasons, it's not considered a technical barrier to inbox placement.

Key considerations

• Prioritize major factors: Marketers should prioritize factors like sender reputation, content quality, and recipient engagement. For instance, consider how subject lines impact deliverability.
• ESP limitations: Understand that many ESPs, including Zoho, have standard header implementations that might not be user-configurable.
• Perception: The "Using Zoho Campaigns" text is generally benign and unlikely to cause recipient distrust or mark messages as spam.
• Header importance: While the X-Mailer header isn't critical, other headers are vital for deliverability and preventing spam. Learn more about email headers in this ultimate guide to email headers.

Key opinions

• Informational purpose: The X-Mailer header's primary function is to simply tell the recipient or receiving server what program was used to send the email.
• Minimal deliverability impact: Experts largely agree that this header does not, by itself, negatively impact deliverability. There's no inherent harm in its presence. This is consistent with what is known about whether X-Headers negatively impact email deliverability.
• Conditional flagging: The only scenario where an X-Mailer header might cause problems is if specific email servers or spam filters are intentionally configured to flag a particular X-Mailer value, often associated with phishing attempts or known malicious software.
• Google's transparency: Google's display of "Using..." is a feature to show the origin of the email, not an indicator of poor deliverability or spam risk. This information about email clients is further explained on the Mutant Mail blog about the X-Mailer header.

Key considerations

• Authentication remains paramount: Ensure robust email authentication (SPF, DKIM, DMARC) is in place, as these are the true technical pillars of deliverability. Proper configuration is essential to boost email deliverability rates.
• ESP control: The ability to remove or modify the X-Mailer header is usually determined by the ESP. In most cases, it's not configurable by the user.
• Reputation signals: Mailbox providers primarily assess sender reputation based on engagement metrics, spam complaints, and adherence to authentication standards, not on the X-Mailer header.
• Header review: While X-Mailer is minor, it is prudent to understand all your email headers. Pay close attention to headers that indicate personalization errors that could be problematic.

Key findings

• Optional header: The X-Mailer header is typically classified as an optional, non-standard (or X-Header) in RFCs, meaning its inclusion is at the discretion of the sending application.
• Informational content: Its purpose is to convey information about the Mail User Agent (MUA) or software responsible for originating the message, such as "Zoho Campaigns".
• No direct deliverability role: RFCs and related documentation do not specify a role for the X-Mailer header in terms of email routing decisions, spam scoring, or inbox placement algorithms.
• Contrast with standard headers: It differs from crucial standard headers like From, To, Date, and authentication headers (SPF, DKIM, DMARC), which are integral to email delivery. Delve deeper into this topic with what RFC 5322 says versus what actually works.

Key considerations

• RFC compliance: Focus on ensuring your email infrastructure complies with relevant RFCs for core headers and authentication mechanisms rather than optional ones. Understanding advanced email authentication is key.
• ESP behavior transparency: While RFCs define the theoretical framework, specific ESPs like Zoho Campaigns may choose to include or omit certain optional headers as part of their service offering.
• Filtering reliance: Spam filters and mailbox providers rely on a complex array of signals, including sender reputation, content analysis, and authentication results, not typically on the identifying information in the X-Mailer header.
• Standard headers: Prioritize the correct configuration and adherence to standards for required email headers, as these are universally evaluated by mail systems. For example, RFC 8058 outlines a new header for one-click unsubscribe, which directly impacts user experience and list hygiene.