How should a sender allocate campaigns across multiple IPs when migrating from an in-house setup?

Key findings

• Volume assessment: A monthly volume of 1 million emails, while significant, might not necessitate four dedicated IPs, as some experts suggest it is not a large volume for that many IPs. ESP policies or client requests often lead to more IPs than strictly required.
• IP consolidation: For the given volume and IP count, it may be more efficient to consolidate campaign types onto fewer IPs, such as one for transactional emails and another for all other marketing and engagement campaigns. This simplifies the IP warming process.
• Reputation management: Separating transactional emails onto their own dedicated IP is a standard best practice to maintain high deliverability, as these emails are critical and usually have higher engagement. This helps to safeguard this vital stream from potential issues with promotional content.
• Subdomain strategy: Utilizing subdomains in conjunction with dedicated IPs allows for more granular reputation management per email stream. For example, managing subdomain reputation is key.

Key considerations

• IP warming timeline: All IPs and subdomains must be properly warmed up, starting with smaller volumes of engaged recipients and gradually increasing. This builds sender reputation with internet service providers (ISPs). You can learn more about IP warming strategies.
• Campaign segregation: Allocate campaigns based on their sending characteristics and recipient engagement levels. Transactional emails should remain separate due to their high importance and expected engagement rates. Promotional and re-engagement campaigns, which often have lower engagement, can be grouped.
• Monitoring: Closely monitor deliverability metrics for each IP and subdomain during the migration and warm-up phases. This includes bounce rates, complaint rates, open rates, and blocklist (blacklist) appearances.
• Flexibility: Be prepared to adjust IP allocation and sending volumes based on performance. Some ISPs respond differently to various sending patterns.

Key opinions

• Volume vs. IPs: For a monthly volume of 1 million emails, 4 dedicated IPs are considered excessive by many marketers. This volume can often be managed effectively with fewer IPs.
• Simplification: It's generally recommended to assign transactional emails to one IP and group all other campaign types (promotional, triggered, newsletters) onto a second IP. This approach simplifies the overall IP warm-up strategy.
• ESP policies: Some ESPs may provide more dedicated IPs than necessary, or clients may request an excessive number. This doesn't always reflect optimal deliverability strategy.
• Reputation isolation: Segregating high-priority, high-engagement transactional emails onto their own IP helps protect their reputation from any potential negative impact from lower engagement or less desired bulk sends. This is a crucial element for boosting email deliverability.

Key considerations

• Warm-up complexity: Warming up 4 IPs simultaneously for a monthly volume of 1 million can be unnecessarily complex and time-consuming. Reducing the number of IPs being warmed up can expedite the migration.
• Campaign grouping: Consider grouping campaigns like promotional, newsletters, customer service, and re-engagement onto a single IP or a pair of promotional IPs if volume demands it. The key is consistent sending volume and engagement per IP.
• Sender reputation: Focus on building a strong sender reputation for the main marketing IP. This involves sending to engaged recipients, monitoring feedback loops, and avoiding spam traps. This contributes to better overall sender reputation with ISPs.
• Subdomain alignment: Ensure that subdomains are properly configured and aligned with the chosen IPs to support reputation segregation and authentication protocols like SPF, DKIM, and DMARC.

Key opinions

• Efficiency over quantity: Experts often recommend fewer dedicated IPs for volumes around 1 million emails per month, as warming and maintaining reputation across many IPs can be more challenging than beneficial.
• Strategic separation: The most critical email types, such as transactional emails, should always be on a separate IP to insulate their deliverability from the potentially more variable performance of marketing emails.
• Harmonized warm-up: Reducing the number of IPs simplifies the IP warming process, allowing for a more focused and controlled ramp-up of sending volume and reputation.
• ISP expectations: ISPs evaluate IP reputation based on consistent sending patterns and engagement. Too many IPs for insufficient volume can lead to inconsistent sending, potentially hindering reputation building.

Key considerations

• Volume distribution: Assess the daily and weekly volume for each campaign type, not just monthly. This informs how to distribute volume across the fewer, optimal IPs to maintain consistent sending habits.
• Reputation tracking: Implement robust monitoring of IP and domain reputation, including blocklist status, during and after migration to quickly identify and address any deliverability issues. This is especially important for new IPs.
• Subdomain purpose: Ensure each subdomain has a clear purpose and is aligned with the specific campaign type and IP it's associated with, reinforcing sender identity and trust.
• Flexibility in scaling: While starting with fewer IPs might be optimal, have a plan for how to scale up (add more IPs) if future email volume significantly increases. This typically applies when volume reaches into the tens of millions monthly, as suggested by GreenArrow Email regarding multiple IP addresses.

Key findings

• Dedicated IP benefits: Documentation often highlights that dedicated IPs allow high-volume senders to build an independent reputation with ISPs, which can be more stable than shared IPs, as noted by Ongage.
• Volume justification: The need for multiple IP addresses is primarily driven by high sending volume and the desire to separate different email streams, as explained by GreenArrow Email.
• Reputation isolation: Transactional emails should ideally be sent from a distinct IP to ensure their consistent delivery, minimizing the risk of marketing-related issues affecting critical communications.
• IP warm-up imperative: All new dedicated IPs, along with associated subdomains, must undergo a structured IP warm-up process to establish a positive sending history with ISPs.

Key considerations

• Phased migration: When migrating, a phased approach is recommended, gradually shifting volume from the in-house setup to the new ESP and IPs. This can be compared to running circuits in parallel during migration.
• Consistent sending: Maintain consistent sending volumes and patterns on each IP once warmed. Erratic sending can negatively impact reputation.
• Subdomain pairing: Pair specific subdomains with specific IPs for different campaign types to clearly delineate sending identities and manage their individual reputations.
• Monitoring tools: Utilize available tools and dashboards from the ESP and ISPs (like Google Postmaster Tools) to monitor deliverability, feedback loops, and reputation health for each IP and domain.