Should I use a backup ESP when my primary ESP is blocked by Spamhaus?

Key findings

• Reputation transfer is difficult: Shifting email volume to a new ESP without proper IP warming on the backup platform can lead to immediate deliverability issues and potentially blacklisting of the new ESP's IPs.
• Underlying issue remains: A Spamhaus listing often points to deeper problems with list hygiene or sending practices, which a backup ESP does not resolve.
• Risk of dual listing: Attempting to evade a blocklist by quickly switching can result in the backup ESP also getting listed, complicating future delisting efforts and possibly leading to account termination.
• Operational complexity: Managing multiple ESPs, especially for disaster recovery, introduces significant operational overhead and processes.

Key considerations

• Proactive hygiene: Focus on maintaining a clean email list and adhering to best practices to prevent blocklistings in the first place.
• Warm-up necessary: Any new IP or domain combination, even on a backup ESP, requires a dedicated warm-up period to build sender reputation.
• Transparency with ESPs: Be upfront with your ESPs about your sending intentions and any strategies involving multiple providers.
• Address root cause: Prioritize resolving the underlying issues that led to the Spamhaus listing, such as poor data quality or spam trap hits. A helpful resource for starting the delisting process can be found on Validity's blog. Also, understanding what causes Spamhaus blacklisting is key.

Key opinions

• Parallel systems preferred: Many marketers use multiple ESPs in parallel for different types of messaging (e.g., marketing versus transactional) rather than a primary/backup setup.
• IP warming challenge: A significant hurdle for a true backup system is the difficulty of keeping a secondary ESP's IPs warm enough to handle a sudden surge in volume without damaging its reputation.
• Reputation risk to backup: Some marketers express concern that a quick switch to a backup ESP after a blocklisting indicates an attempt to "spam" and will likely lead to the backup ESP being blocked as well.
• Disaster recovery vs. deliverability: The concept of redundancy might be feasible for system outages (disaster recovery), but not as a solution for inherent deliverability problems caused by list quality.

Key considerations

• Volume distribution: For effective disaster recovery, consider distributing email volume across two platforms or data centers continuously, even if it is 50/50.
• Shared vs. dedicated environments: Evaluate the benefits and risks of both shared and dedicated IP environments when considering multiple ESPs, as each has its own challenges regarding algorithm changes.
• Sales team education: Marketers sometimes face pressure from sales or business teams to find quick fixes like a backup ESP, requiring education on deliverability realities.
• Focus on data quality: The core issue behind Spamhaus listings is often poor database hygiene, requiring significant effort on data cleansing and robust opt-in processes. Learn how to check and improve your email sender reputation.

Key opinions

• Not a functional solution: Experts agree that a backup ESP is not a viable solution for Spamhaus issues, as it does not address the root cause of the listing (for example, poor list quality).
• IP warming is critical: It is nearly impossible to keep a backup ESP sufficiently "warm" to handle a sudden influx of volume without damaging its new IPs or domain reputation.
• Spamhaus listings indicate bad data: A Spamhaus listing strongly suggests that a significant portion of the sender's database is "valueless and toxic," requiring serious data cleansing.
• Increased delisting difficulty: Attempting to evade a blocklist by switching ESPs can be seen as deliberate evasion, making future delisting processes far more challenging and potentially leading to DBL (Domain Blocklist) listings, which are harder to resolve than SBL (Spamhaus Block List) listings.

Key considerations

• Address the database: The primary focus should be on cleaning and validating the email database that triggered the Spamhaus listing. This helps fix why emails go to spam.
• Implement verification: Ensure all data collection points have robust verification mechanisms, such as CAPTCHAs and confirmed opt-in (double opt-in).
• Seek assistance for delisting: If listed, work directly with Spamhaus or your ESP to resolve the issue, as this is typically faster and more effective than switching providers. You can also get help with a Spamhaus listing delisting.
• Understand blocklist triggers: Recognize that Spamhaus listings are usually due to spam traps and list hygiene failures, not random occurrences affecting even "good guys."

Key findings

• Spamhaus delisting process: Documentation from Spamhaus and related services outlines a clear delisting process that requires remediation of the underlying cause, not just moving to a different sender.
• Focus on source of spam: Technical guidelines underscore that successful email delivery relies on maintaining a clean sending reputation by avoiding known spam indicators.
• Importance of list quality: Documentation frequently stresses that accurate and consented subscriber lists are fundamental to avoiding spam traps and complaints that lead to blocklistings.
• Authentication protocols: Proper implementation of SPF, DKIM, and DMARC is crucial for demonstrating legitimacy and can help mitigate the impact of some blocklistings, although they do not prevent bad sending practices.

Key considerations

• Regular list cleaning: Implement automated and manual processes for identifying and removing inactive or problematic email addresses (for example, spam traps).
• Monitor feedback loops: Utilize feedback loops (FBLs) provided by major internet service providers (ISPs) to identify users marking emails as spam and remove them from your lists.
• Review sending patterns: Analyze sending volume, frequency, and content to identify any patterns that might trigger spam filters or blocklists.
• Understand blocklist criteria: Familiarize yourself with the specific criteria that different blocklists (like Spamhaus) use to list IPs and domains. More information on the role of ESPs in blocking spam can be found at Abusix. Additionally, understand how email blacklists actually work.