Summary
Recipients exceeding hourly email limits when BCC is used is a multifaceted issue. A core problem stems from how ESPs and receiving servers handle BCC. ESPs might not log BCC recipients correctly, misattributing bounces and skewing deliverability metrics. More broadly, both ESPs and receiving servers treat BCC'd recipients similarly to 'To' recipients, leading to a rapid consumption of sending limits. The practice of BCC itself, particularly in high volumes, is flagged as a spam indicator, resulting in stricter filtering and potential blocks. This association is due to BCC masking recipients, hindering recipient list hygiene, and often correlating with unengaged addresses. Technical issues also contribute, such as BCC exacerbating authentication failures (SPF, DKIM) in certain forwarding setups. Finally, BCC's facilitation of sending to many recipients can overload servers, triggering rate limiting and temporary sending restrictions imposed by platforms like Microsoft EOP, Google Workspace, and AWS SES.
Key findings
- Logging Errors: ESPs may misattribute bounces from BCC recipients, skewing deliverability metrics.
- Limit Consumption: BCC'd recipients count toward sending limits, exhausting quotas quickly.
- Spam Signal: High-volume BCC usage is a red flag for spam filters, impacting deliverability.
- Hygiene Issues: BCC hinders list hygiene practices due to lack of individual tracking.
- Authentication Problems: BCC can worsen SPF/DKIM failures with specific forwarding setups.
- Server Overload: BCC facilitates high-volume sending, potentially overloading servers.
Key considerations
- ESP Configuration: Ensure ESPs accurately log and track BCC'd recipients.
- Sending Alternatives: Consider alternatives to BCC for mass emailing (e.g., dedicated ESPs).
- List Management: Implement robust list management, segmentation, and cleaning processes.
- Authentication: Verify correct SPF/DKIM settings to minimize authentication failures.
- Volume Control: Monitor and manage sending volume to avoid server overload.
- Transparent Practices: Adopt transparent emailing practices to build trust and avoid spam flags.
What email marketers say
9 marketer opinions
Using BCC can lead to recipients exceeding hourly email limits due to several factors. Email Service Providers (ESPs) often treat BCC'd recipients similarly to regular recipients, causing sending IP addresses to reach rate limits faster. High volumes of BCC emails, especially to unengaged or invalid addresses, can negatively impact sender reputation, leading to aggressive rate limiting and potential blocking by ISPs. The practice can trigger spam filters as it masks recipients and can look like a spamming technique. Moreover, sending a massive number of emails in a short period (facilitated by BCC) can overload mail servers and trigger rate limiting. Finally, when used with certain email forwarding setups, BCC can lead to SPF and DKIM authentication failures, further contributing to deliverability problems and rate limiting.
Key opinions
- Rate Limit Impact: BCC usage accelerates hitting hourly sending limits as each BCC'd recipient counts toward the IP's limit.
- Reputation Damage: High volumes of BCC emails, particularly to unengaged addresses, harm sender reputation.
- Spam Trigger: BCC can trigger spam filters due to its association with masking recipients, resembling spamming techniques.
- Server Overload: The large volume of emails sent via BCC can overload mail servers, leading to rate limiting.
- Authentication Issues: Using BCC with specific forwarding setups can cause SPF and DKIM authentication failures.
Key considerations
- List Management: Ensure proper list management practices when using BCC to minimize the risk of sending to unengaged or invalid addresses.
- Sender Reputation: Monitor and maintain sender reputation to avoid being flagged as a spammer due to high BCC volumes.
- Alternative Methods: Consider alternative methods for sending emails to large groups that allow for individual tracking and engagement, such as using an ESP.
- Authentication Setup: Verify that email authentication protocols (SPF, DKIM) are properly configured to prevent deliverability issues when using BCC.
- Sending Volume: Be mindful of sending volume when using BCC to avoid overloading mail servers and triggering rate limits.
Marketer view
Email marketer from SparkPost Support explains that if BCC recipients are largely unengaged or invalid addresses, it can significantly degrade sender reputation. ISPs may interpret this as a sign of spam, leading to aggressive rate limiting or blocking.
13 Nov 2021 - SparkPost Support
Marketer view
Email marketer from Reddit explains that using BCC extensively can trigger spam filters and throttling mechanisms because it masks the true recipients and can look like a spamming technique, especially if the list is not properly managed.
19 Jan 2023 - Reddit
What the experts say
4 expert opinions
Recipients can exceed hourly email limits when BCC is used due to several factors highlighted by experts. A key issue arises when ESPs fail to properly log BCC'd recipients, leading to incorrect bounce attribution to the 'To' line recipients and potentially triggering rate limits. The practice of BCC itself, especially extensive use, is associated with spam-like behavior and can lead to deliverability problems and blocks by receiving servers. Hiding recipients from each other prevents the server from getting a full view of the email recipients, which increases the likelihood of emails being marked as spam, and also hinders list hygiene.
Key opinions
- ESP Logging Issues: ESPs failing to log BCC'd recipients and misattributing bounces can lead to inaccurate deliverability reporting and potential rate limiting.
- Spam Association: Extensive BCC usage is often linked with spam practices, leading to deliverability issues and blocks.
- Reduced Visibility: BCC hides recipients, preventing servers from having a complete view of the email's recipient list, increasing spam likelihood.
- List Hygiene Neglect: The use of BCC hinders list hygiene practices because engagement cannot be tracked individually.
Key considerations
- Proper ESP Configuration: Ensure the ESP is properly configured to accurately log and track BCC'd recipients.
- Alternative Methods: Consider using alternative methods, like dedicated email marketing platforms, instead of BCC for mass emailing.
- List Management Practices: Implement robust list management practices, including regular cleaning and segmentation, to improve deliverability.
- Transparency: Prioritize transparency in email communications to build trust with recipients and avoid being flagged as spam.
Expert view
Expert from Spam Resource explains that using BCC hides recipients from each other which prevents the server from getting a full view of the email recipient which increases the likely hood of the email getting marked as spam. It also reduces list hygiene.
4 Jan 2022 - Spam Resource
Expert view
Expert from Word to the Wise explains that extensive use of BCC can lead to deliverability problems and potential blocks as it is often associated with spam practices and may not allow for proper list management and engagement tracking.
3 Nov 2022 - Word to the Wise
What the documentation says
4 technical articles
Documentation from various email platforms and standards organizations indicates that using BCC can contribute to recipients exceeding hourly email limits. Exchange Online Protection (EOP), Google Workspace, and AWS SES all implement limits to prevent spam and abuse, which can be triggered by a large number of BCC recipients in a single email. Even though RFC 5322, which outlines SMTP standards, doesn't explicitly address BCC, it sets limits on message size and recipient numbers, potentially impacting large BCC sends and causing deliverability issues and rate limiting. Essentially, the practice of sending to a large number of recipients via BCC can quickly exhaust these predefined limits, leading to temporary sending restrictions and delivery problems.
Key findings
- Spam Prevention: Email platforms implement limits to prevent spam and mass mailing abuse, impacting BCC usage.
- Limit Trigger: A large number of BCC recipients in a single email can trigger spam prevention limits.
- Standard Limitations: SMTP standards set limits on message size and recipient numbers, affecting large BCC sends.
- Quota Consumption: All recipients, including those BCC'd, count towards sending quotas in platforms like AWS SES.
Key considerations
- Limit Awareness: Be aware of sending limits imposed by email platforms when using BCC.
- Recipient Number: Avoid including a large number of recipients in a single email when using BCC.
- Compliance: Ensure compliance with SMTP standards regarding message size and recipient numbers.
- Quota Monitoring: Monitor sending quotas to avoid exceeding limits when using BCC.
Technical article
Documentation from AWS outlines the sending limits of SES. While not explicitly about BCC, it notes that all recipients (To, CC, and BCC) count towards your sending quota. Using BCC heavily can lead to quickly reaching these limits.
23 May 2023 - AWS Documentation
Technical article
Documentation from Microsoft Docs explains that Exchange Online Protection (EOP) employs various limits to prevent spam and mass mailing abuse. These limits could be triggered if a large number of BCC recipients are included in a single email, causing the system to flag it as potential spam.
4 Jul 2022 - Microsoft Docs
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