Why is one sales rep's email blocked when others aren't?

Key findings

• Recipient control: Email clients and recipients ultimately determine whether an email is considered spam, regardless of sender intent or content. A higher rate of recipients marking a particular rep's emails as spam can quickly degrade individual sender reputation.
• Individual reputation: Even with a neutral domain or IP reputation, individual sender reputation can be negatively affected by specific sending patterns or recipient feedback unique to that sales rep.
• Content specifics: Subtle differences in email content, such as specific URLs, attachments, or even the email signature, can trigger recipient-side security rules, leading to blocks. This is especially true with sophisticated spam filters (like Mimecast).
• Target audience: The specific list of recipients targeted by one rep might be more sensitive or prone to blocking compared to others, even if the general email list source is shared across the team.
• Hidden tracking: Platforms like Google are increasingly flagging hidden tracking pixels as dangerous, which could impact deliverability for some senders more than others. Communications Edge explains more about Google's measures to mark sales outreach emails as spam.

Key considerations

• Analyze bounce messages: Examine specific SMTP error codes (e.g., 550, 554) to understand the reason for the block, as these often provide clues about content issues or recipient-specific policies. For example, some Mimecast errors can be very specific about why an email is rejected.
• Review individual sending behavior: Even if the template is the same, subtle variations in personalization, timing, or direct recipient interactions could be contributing factors. Are they sending too many emails at once? Nutshell shares insights on sales email mistakes that lead to spam.
• Check email content variations: Scrutinize the exact content of the blocked emails, looking for unique URLs, formatting quirks, or different tracking mechanisms not present in other reps' emails.
• Address recipient feedback: If a recipient actively marks an email as spam, this strong negative signal can quickly affect future deliverability from that specific sender (or address). Consider stopping outreach to organizations where a rep is consistently blocked.
• Monitor specific blocklists: While IP/domain reputation might be neutral, an individual email address could be triggering internal, private blacklists at specific recipient organizations.

Key opinions

• Recipient's decision: The sender cannot dictate if an email is spammy; only the recipient can make that call. This highlights that blocking is often a correct function of the email client.
• Spam reports: If a rep's emails are being marked as spam by recipients, this is a strong negative signal. High numbers of these this is spam clicks will affect deliverability, sometimes more so than passively landing in the spam folder.
• Content variations: Even with plain text emails, minor content differences or the presence of specific URLs or signatures can trigger receiver-side security rules.
• List source: The way email addresses are collected or the quality of the email list source can be a significant red flag, leading to deliverability problems.
• Gmail settings: There are no settings within Gmail itself that can force third-party email receivers to accept messages, as their acceptance criteria are based on their own content and local settings. For more insights into Gmail blocking, see our article on why emails are suddenly rejected by Gmail.

Key considerations

• Review recipient organization: If a specific rep is consistently blocked by a particular recipient organization (e.g., via Mimecast security rules), it might be worthwhile to stop sending to that organization to avoid further reputation damage.
• Sender name perception: Consider if the sales rep's name or personal appeal might inadvertently lead to more direct negative feedback (like spam reports) from the target audience compared to other team members.
• Aggressive outreach: Mass-emailing a high number of people at once, especially in sales outreach, often results in emails landing in the spam folder. This is a common sales email mistake.
• Unsubscribe problematic recipients: If a person is marking emails as spam, the best course of action is to unsubscribe them. This prevents further negative signals.

Key opinions

• Receiver-side blocking: Blocking is typically initiated by the receiver, based on their specific security rules or content policies. This means there are no Gmail settings to override a third-party receiver's decision.
• Content triggers: Elements like specific URLs, different signatures, or particular phrases within the email can trigger security blocks (e.g., Mimecast's 554 security error).
• Email list source: A significant majority (as high as 99%) of deliverability problems can be traced back to how email addresses are collected. Using questionable email list sources is a major red flag.
• Mail admin irritation: Persistent unwanted emails from a sales rep can irritate a recipient's mail administrator, leading to a deliberate block of the sender or even the entire sending organization.
• Intermittent IP reputation: For senders using services like Gmail, deliverability issues can be intermittent due to a shared IP infrastructure where users receive different IPs at different times, potentially impacting their IP reputation unexpectedly.

Key considerations

• Unsubscribe problematic contacts: Immediately unsubscribe individuals who are blocking messages or marking them as spam. This is crucial for mitigating reputation damage.
• Examine sending context: Investigate the specific context of the blocked messages, including the exact error codes (e.g., 550, 554), as these provide direct reasons for non-delivery from the recipient's system.
• Content review: Thoroughly review the content of the problematic rep's emails for any unique URLs or elements that might trigger security filters, even if the general template is the same.
• Consider recipient organizations: If a particular recipient organization is consistently blocking one rep, it might be advisable to cease sending to that organization to avoid escalating issues.

Key findings

• SMTP error codes: Error messages like 550 or 554 are often provided by receiving mail servers, indicating permanent failures and specific reasons for the block, which can relate to reputation or email setup (e.g., Mimecast SMTP Error Codes).
• Security policies: Receiving email platforms (like Mimecast) implement various security policies that scan inbound messages for potential threats or policy violations. Content such as URLs or attachments can trigger these policies, resulting in a 554 security error.
• Recipient server's decision: The receiving mail server ultimately decides whether to accept an email, based on its own internal configurations and reputation algorithms. This means a block is a direct action by the recipient's system.
• Content scanning: Emails are often subjected to deep content scanning for suspicious patterns, malware, or policy violations. Even plain text emails can be blocked if they contain elements deemed malicious or policy-violating by advanced filters.

Key considerations

• Consult error messages: Always refer to the specific bounce or rejection message from the receiving server. These messages are designed to indicate the exact reason for non-delivery and often point to relevant documentation.
• Understand Mimecast errors: For specific providers like Mimecast, detailed documentation on their SMTP error codes (e.g., their SMTP Error Codes article) is invaluable for troubleshooting. The 554 errors often refer to security policies being triggered, while 550 errors may indicate a permanent rejection.
• Review email content and headers: Even for plain text, scrutinize all components including headers, embedded links, and sender authentication records (SPF, DKIM, DMARC) for any discrepancies that might trigger automated blocks. Check out our guide on why emails go to spam.
• Contact recipient: Documentation often implies that direct communication with the recipient or their IT department might be necessary to understand specific, localized security rules that are causing the blocks.