Summary
When migrating an existing email domain to a new Email Service Provider (ESP), a warm-up period is essential, regardless of your domain's established reputation. This is because the new ESP utilizes different sending IP addresses that need to build trust with mailbox providers. While you cannot use the identical DKIM record across multiple ESPs, the DKIM standard allows a single domain to send via different providers by employing unique selectors for each ESP, meaning you will have separate DKIM records for each service.
Key findings
- Warm-up for Existing Domains: Yes, even an existing email domain with a good reputation requires a warm-up period when moving to a new Email Service Provider (ESP). This is crucial because the new ESP uses different sending IP addresses and infrastructure, which need to establish their own reputation and trust with mailbox providers.
- DKIM for Multiple ESPs: You cannot use the exact same DKIM record across multiple ESPs. However, you can use DKIM with multiple ESPs for a single domain by configuring distinct DKIM records, each with its own unique 'selector' provided by the respective ESP. This allows each service to sign emails from your domain independently.
Key considerations
- IP vs. Domain Reputation: Email deliverability is heavily influenced by both domain and IP address reputation. While your domain might have an established, positive history, a new Email Service Provider (ESP) will use different sending IP addresses. These new IPs lack a pre-existing reputation, necessitating a warm-up period to build trust with mailbox providers, independent of your domain's standing.
- Gradual Volume Increase: The warm-up process for new sending infrastructure, even with an established domain, involves a slow and gradual increase in email volume. It is recommended to start by sending to highly engaged subscribers and progressively expand to larger segments, allowing mailbox providers to recognize and trust the new sending patterns and IP addresses over time. This helps prevent flagging by spam filters.
- DKIM Selector Mechanism: The DKIM standard utilizes a 'selector' mechanism, which allows a single domain to have multiple unique DKIM keys published in its DNS records. Each ESP you use will typically provide its own distinct DKIM key pair and a unique selector. This enables each ESP to independently sign emails from your domain, even though you are using a single domain across multiple services.
- Separate DKIM Records: You cannot use the exact same DKIM record, meaning the same selector and public key, across multiple ESPs. Instead, you will configure separate DKIM records in your domain's DNS for each ESP. Each record will have a unique selector provided by the respective ESP, allowing for proper authentication of emails sent through different providers while maintaining the integrity of your domain's sending identity.
What email marketers say
12 marketer opinions
Migrating an email domain to a new Email Service Provider (ESP) necessitates a strategic warm-up period, even if your domain already boasts a strong sending history. This vital step is due to the new ESP's distinct sending infrastructure and IP addresses, which require time to establish their own reputation with mailbox providers. While you cannot employ an identical DKIM record across various ESPs, the DKIM protocol is designed to accommodate this by allowing for unique selectors. This means a single domain can effectively send emails through multiple providers, each with its own specific DKIM record and selector.
Key opinions
- New ESP, New IPs, Warm-up: Migrating an existing, reputable domain to a new Email Service Provider (ESP) always necessitates a warm-up period. This is because the new ESP provides different sending IP addresses and infrastructure, which lack an established reputation and must gradually build trust with mailbox providers, regardless of the domain's prior history.
- DKIM with Multiple Selectors: It is not possible to use the exact same DKIM record, meaning the same selector and public key, across multiple Email Service Providers (ESPs). However, the DKIM protocol allows a single domain to send email through various ESPs by using different selectors. Each ESP will have its own unique DKIM key pair, requiring a separate DKIM record with a distinct selector to be published in your domain's DNS.
Key considerations
- Reputation and New IPs: Email deliverability reputation is significantly tied to the specific IP addresses used for sending. When transitioning to a new Email Service Provider (ESP), your domain will be associated with their distinct sending infrastructure and IP pool. These new IPs must establish their own reputation, even if your domain has a long-standing, positive history.
- Gradual Warm-up Strategy: A key aspect of warming up a new IP and domain combination is a slow, gradual increase in sending volume. Begin by sending to your most engaged subscribers, then progressively expand to larger segments. This measured approach allows mailbox providers to observe consistent, positive sending behavior from the new infrastructure, which is crucial for building trust and avoiding spam filters.
- DKIM Selector Uniqueness: To use DKIM with multiple Email Service Providers (ESPs) for a single domain, each ESP will require you to publish a unique DKIM record in your domain's DNS. These records are differentiated by unique 'selectors' provided by each ESP, which allow mailbox providers to look up the correct public key to verify the sender's signature, even when mail originates from different services.
- Advantages of Multiple DKIMs: Using unique DKIM selectors and records for each Email Service Provider (ESP) you use is not only a technical necessity but also a good practice. This approach ensures that all email streams from your domain, whether sent for marketing or transactional purposes, are properly authenticated. It reinforces your domain's legitimacy and can contribute to better overall deliverability performance.
Marketer view
Email marketer from Email Geeks explains that any new combination of domain and IP addresses should be introduced with at least some ramp-up, even if they have independent histories, and it should not be skipped entirely.
31 Oct 2023 - Email Geeks
Marketer view
Email marketer from Email Geeks explains that you need to warm up the mail stream, which is approximated by an IP/domain tuple. Shortcuts, such as using the same DKIM d=, can affect how fast you warm up, but not whether you need to.
7 Mar 2023 - Email Geeks
What the experts say
3 expert opinions
Even with an established email domain, a warm-up phase remains essential when transitioning to a new Email Service Provider (ESP). This is because the new ESP introduces different IP addresses that must build their own sending reputation with mailbox providers. Regarding DKIM, while a single domain can utilize multiple ESPs, it's not feasible to share the exact same DKIM private key or record. Instead, each ESP will require its own distinct DKIM public key and a unique 'selector' published in your DNS, enabling independent email signing.
Key opinions
- Warm-up New ESP IPs: Migrating an established email domain to a new Email Service Provider (ESP) requires a warm-up period. This is vital because the new ESP uses different IP addresses, which must independently build a positive sending reputation with mailbox providers, regardless of your domain's prior standing.
- Unique DKIM Selectors: Using the same DKIM private key or a single DKIM record across multiple ESPs for a single domain is not possible or recommended. Instead, each ESP will provide a unique DKIM public key and a distinct 'selector', necessitating separate DKIM records in your DNS to allow independent email signing by each provider.
Key considerations
- New IP Reputation: While your email domain might have a stellar reputation, the new IP addresses provided by a new Email Service Provider (ESP) start with a fresh slate. It is these IP addresses that need to earn the trust of mailbox providers, making a warm-up strategy critical for deliverability.
- Strategic Volume Increase: A successful warm-up involves carefully increasing your email sending volume on the new ESP's infrastructure. Begin by targeting your most engaged segments to send positive signals to mailbox providers, then progressively expand your audience, allowing the new IP addresses to establish a reliable sending history.
- DKIM Key Management: When utilizing multiple Email Service Providers (ESPs) for a single domain, you will manage multiple DKIM records in your DNS. Each ESP supplies its own unique public key and a distinct 'selector', ensuring that emails signed by different providers can be independently verified, thus maintaining email authentication integrity.
- Ensuring Authentication: Properly configuring unique DKIM records for each Email Service Provider (ESP) is paramount for robust email authentication. This practice confirms that emails originating from your domain, even through various sending systems, are legitimate, which is crucial for bypassing spam filters and enhancing deliverability.
Expert view
Expert from Email Geeks explains that you can use the same DKIM 'd=' tag with different selectors across multiple ESPs.
24 Aug 2023 - Email Geeks
Expert view
Expert from Word to the Wise confirms that even when migrating an existing domain to a new ESP, a warm-up period is still crucial. While the domain has an existing reputation, the new IP addresses provided by the new ESP need to establish their own reputation with mailbox providers. It recommends starting with engaged segments and gradually increasing volume to build trust for the new sending infrastructure.
27 Aug 2023 - Word to the Wise
What the documentation says
5 technical articles
For an established email domain, moving to a different Email Service Provider (ESP) still necessitates a warm-up period. This is because the new ESP introduces a distinct set of sending IP addresses that must independently build trust and reputation with mailbox providers. While you cannot use the exact same DKIM record across multiple ESPs, the DKIM standard allows for this scenario by utilizing unique 'selectors,' meaning each ESP will require its own specific DKIM record with a unique identifier published in your domain's DNS.
Key findings
- Warm-up Essential for New IPs: Even an existing, reputable email domain requires a warm-up period when migrating to a new Email Service Provider (ESP). This is because the new ESP uses different IP addresses and sending infrastructure, which must independently establish their own positive reputation with mailbox providers, regardless of the domain's prior standing.
- Multiple DKIMs via Selectors: It is not possible to use the identical DKIM record across multiple ESPs for a single domain. However, the DKIM standard is designed to accommodate this by allowing for unique selectors. This means you will configure separate DKIM records, each with its own distinct selector provided by the respective ESP, enabling your domain to send authenticated email through various providers.
Key considerations
- Establishing New IP Trust: While your email domain maintains its established reputation, the new IP addresses provided by a new Email Service Provider (ESP) begin with a fresh, unestablished reputation. It is critical for these new IPs to build trust with mailbox providers, making a structured warm-up process essential for optimal deliverability.
- Phased Sending Rollout: A successful warm-up involves a controlled, phased increase in email sending volume from the new ESP. Start by targeting your most active subscribers to send positive engagement signals, then gradually expand to larger segments. This systematic approach allows the new IP addresses to establish a reliable sending history and avoid being flagged by spam filters.
- DKIM Selector Function: The DKIM standard uses 'selectors' to differentiate between multiple DKIM keys for a single domain. Each Email Service Provider (ESP) you use will provide its own unique selector and corresponding public key. This mechanism allows a single domain to utilize multiple sending services simultaneously, each with its independently verifiable signature.
- Individual DKIM Configurations: You will need to set up individual DKIM records for each Email Service Provider (ESP) you utilize, not a single shared one. Each record will include the unique selector and public key provided by that specific ESP, ensuring that emails sent through different providers are properly authenticated and maintain your domain's sending legitimacy.
Technical article
Documentation from SendGrid Documentation explains that while domain reputation is persistent, IP reputation is tied to the specific sending infrastructure. When an existing domain moves to a new ESP, it uses new (shared or dedicated) IP addresses. Therefore, a warm-up period is recommended to establish a positive sending reputation for these new IP addresses with mailbox providers, despite the domain's existing standing.
16 Feb 2023 - SendGrid Documentation
Technical article
Documentation from IETF RFCs explains that the DKIM standard (RFC 6376) utilizes selectors to distinguish between multiple DKIM keys published for a single domain. This design inherently supports scenarios where a domain uses multiple sending services (ESPs), each requiring its own unique DKIM key pair and corresponding public key published under a distinct selector in DNS. Thus, an organization can have multiple DKIM records for one domain, one for each ESP.
23 Sep 2022 - IETF RFCs
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