Is it common for agencies to use one ESP with separate IPs per client, and does it impact email deliverability?

Key findings

• Common practice: Agencies frequently adopt a single ESP, leveraging white-label systems to manage distinct client accounts, often with dedicated IPs.
• Operational efficiency: Centralizing with one ESP streamlines internal processes, reduces the need to master multiple platforms, and can lead to economies of scale pricing.
• Deliverability segmentation: Using separate dedicated IPs for each client helps isolate their sending reputations. This means a deliverability issue (e.g., a blocklist placement) for one client is less likely to affect others, a concept also explored when considering separating transactional and marketing emails.
• ESP support: Agencies often receive dedicated support from their ESP due to the significant volume and value of their consolidated client accounts.

Key considerations

• Volume requirement: Dedicated IPs require sufficient sending volume to maintain a warm reputation. Agencies with many low-volume clients might find dedicated IPs suboptimal, as discussed in the context of IP warming strategies. If volume is low, a shared IP might be more appropriate initially.
• Configuration: Proper DKIM and SPF authentication must be meticulously set up for each client’s sending domain to ensure proper deliverability and avoid spoofing.
• Client isolation: The ESP must provide robust mechanisms (sub-accounts, different IP ranges/pools) to ensure client data separation and prevent accidental cross-sending.
• Monitoring: Continuous monitoring of each client's IP and domain reputation is essential to proactively identify and address deliverability issues, especially when considering how IP and domain affect sender score.

Key opinions

• Common and manageable: Many marketers have experienced this setup and view it as a fairly common and manageable practice, especially with white-label ESP options.
• Data isolation is key: The primary concern is ensuring strict data separation between clients to prevent accidental cross-pollination of recipient lists or content.
• Operational advantages: Mastering one ESP deeply is more efficient than managing several, offering significant operational benefits to an agency.
• IP reputation: Marketers appreciate that dedicated IPs help maintain independent sending reputations for each client, preventing one client's issues from affecting another.

Key considerations

• Internal controls: Agencies must implement robust internal controls to ensure client data remains segregated and prevent errors, such as sending emails for one client to another client's customer base.
• Sub-account management: It's crucial that the ESP provides flexible sub-account or profile management features to properly isolate each client's sending environment.
• Deliverability transparency: Agencies should have clear visibility into the deliverability metrics and reputation of each client’s dedicated IP, which is vital for preventing emails from going to spam.
• IP warming strategy: Each new dedicated IP for a client will require a proper IP warming process to build its reputation effectively.

Key opinions

• White-label systems: Experts confirm the existence of ESP white-label systems designed for agencies, allowing for the assignment of dedicated IPs to sub-accounts.
• Volume dependency: The effectiveness of dedicated IPs is volume-dependent. Low-volume clients on dedicated IPs may not perform optimally, suggesting that the decision should be client-specific.
• Deliverability success: Multiple measures can be taken within a single ESP platform to ensure the security and deliverability success of individual clients, even if they're on the same platform.
• Flexibility is key: ESPs offering flexibility in sub-account management and IP assignment are highly valued for their ability to cater to diverse client needs.

Key considerations

• IP pool management: Agencies should inquire about the ESP's ability to assign IPs from different ranges or pools to further diversify and protect client sending reputations. This impacts how ESPs impact deliverability on dedicated IPs.
• Sender score impact: Maintaining a good sender score for each IP is paramount, and agencies need to proactively manage engagement metrics to achieve this. If a dedicated IP sees blocklist placements, it can severely impact deliverability for that client.
• Reputation isolation: The benefit of dedicated IPs lies in isolating deliverability reputations. This strategy helps prevent a problematic sender from negatively affecting others within the agency's portfolio, a consideration often made when deciding why and how many IP addresses to use.
• Client-specific needs: The decision to use a dedicated IP versus a shared IP for each client should be based on their specific sending volume, list quality, and campaign type.

Key findings

• Reputation segmentation: Each IP address maintains its own deliverability reputation, meaning segmenting mail streams by IP address keeps the reputation of each isolated.
• ISP algorithms: Internet Service Providers (ISPs) use complex algorithms to filter incoming emails, and a successful IP warming strategy, often enabled by dedicated IPs, directly impacts deliverability.
• Authentication standards: For multiple IP addresses and distinct sending entities, proper email authentication (SPF, DKIM, DMARC) for each domain is critical to confirm sender legitimacy.
• Mail stream separation: To effectively separate mail streams, documentation advises using different subdomains, IPs, and DKIM for each type of email or client.

Key considerations

• Impact of negative signals: Sending low-engagement or spammy emails can negatively impact the reputation of new IP addresses and hurt deliverability if not properly managed, as outlined in guides about why emails go to spam.
• Transactional vs. marketing: Many sources recommend separating transactional emails from marketing emails by using different domains or IPs to ensure critical transactional emails are not impacted by marketing deliverability issues.
• Monitoring and testing: Regular email deliverability tests and monitoring are crucial to identify and address any issues promptly, a practice highlighted in guides on how to run a deliverability test.
• Sender quality score: ISPs like Gmail use sender quality scores to determine email deliverability. This score is significantly influenced by IP and domain reputation, underscoring the importance of managed dedicated IPs.