Will changing the sending subdomain impact email deliverability and require a new warm-up process?

7 Marketer opinions 4 Expert opinions 4 Technical articles 6 Resources

Summary

Experts and documentation from various sources (Email Geeks, Google, SendGrid, Mailjet, Amazon SES, Spamresource.com, Wordtothewise.com, Reddit, StackExchange, Gmass, MailerLite, and Moosend) overwhelmingly confirm that changing the sending subdomain impacts email deliverability and requires a new warm-up process. A new subdomain does not inherit the reputation of its parent domain, necessitating a separate warm-up to establish its own sending reputation with ISPs. This involves gradually increasing sending volume, initially targeting highly engaged recipients. Failure to warm up the subdomain can negatively impact deliverability, as ISPs need to build trust with the new sending source. Treat the new subdomain as a completely new domain and follow domain-warming best practices to maintain a positive sender reputation.

Key findings

Deliverability Impacted: Changing the sending subdomain negatively impacts email deliverability if not warmed up properly.
Warm-up Required: A new warm-up process is essential for a new sending subdomain.
No Reputation Inheritance: Subdomains do not automatically inherit the reputation of their parent domain.
New Sending Source: ISPs view a new subdomain as a new sending source that requires establishing trust.
Domain Warming Crucial: Domain warming is crucial for building a positive sender reputation.
Treat as New Domain: Treat the new subdomain as a new domain from a deliverability perspective.

Key considerations

Gradual Volume Increase: Gradually increase sending volume during the warm-up process to avoid triggering spam filters.
Engaged Audience Targeting: Initially target highly engaged recipients to build a positive sending reputation.
Monitor Deliverability: Closely monitor deliverability metrics (bounce rates, spam complaints, inbox placement) during and after warm-up.
Content Quality: Ensure high-quality and relevant content to minimize spam complaints.
Follow Best Practices: Adhere to email sending best practices (authentication, list hygiene) to improve deliverability.

What email marketers say
7Marketer opinions

Changing the sending subdomain significantly impacts email deliverability and necessitates a new warm-up process. Email marketers across various platforms (Email Geeks, Reddit, StackExchange, Gmass, MailerLite, and Moosend) agree that a new subdomain, even with an established parent domain, requires building its sender reputation from scratch. This involves gradually increasing sending volume and targeting highly engaged audiences to establish trust with ISPs.

Key opinions

Deliverability Impact: Changing subdomains negatively affects deliverability if not warmed up properly.
Warm-up Required: A new warm-up process is essential for any new sending subdomain.
Reputation: Subdomains do not inherit the parent domain's reputation automatically; they need to build their own.
Treat as New Domain: A new subdomain should be treated as a new sending domain regarding the deliverability impact.
Warming Advice: Warm up a new sending domain, including the amount of emails to send each day and the process for increasing volume.
Warming Strategies: Recommends sending low volume emails to a highly engaged audience, and slowly increasing volume each day.
Closely Related: Domain reputation is closely related to deliverability, and it's crucial to warm up a new domain to establish a positive sender reputation.

Key considerations

Gradual Increase: Increase sending volume gradually to avoid triggering spam filters and damaging reputation.
Engaged Audience: Focus initial sending to highly engaged subscribers to generate positive signals for ISPs.
Warming Schedule: Follow a structured warm-up schedule, increasing volume daily or weekly based on performance.
Monitor Deliverability: Closely monitor deliverability metrics (bounce rates, spam complaints, placement) and adjust the warm-up strategy as needed.
Content Quality: Ensure content is high quality and relevant to avoid spam complaints during the warm-up phase.

Marketer view

Email marketer from MailerLite describes what domain warming is, and why you should warm up a new domain. Recommends sending low volume emails to a highly engaged audience, and slowly increasing volume each day.

July 2022 - MailerLite

Marketer view

Marketer from Email Geeks confirms that changing the sending domain impacts deliverability.

June 2024 - Email Geeks

Marketer view

Email marketer from Gmass shares advice on warming up a new sending domain, including the amount of emails to send each day and the process for increasing volume.

May 2023 - Gmass

Marketer view

Email marketer from EmailGeek shares that changing subdomains will impact deliverability and require a new warm up process.

September 2022 - EmailGeek

Marketer view

Email marketer from StackExchange responds that when using a new subdomain, deliverability may be affected negatively if it's not properly warmed up. Treats the subdomain like a brand new domain in terms of the deliverability impact.

January 2025 - StackExchange

Marketer view

Email marketer from Reddit explains that even with an established parent domain, a new subdomain used for sending email requires a warm-up period. Sending volume should be gradually increased to build a positive sender reputation with ISPs.

January 2022 - Reddit

Marketer view

Email marketer from Moosend mentions that domain reputation is closely related to deliverability. Moosend states that it's crucial to warm up a new domain to establish a positive sender reputation.

September 2023 - Moosend

What the experts say
4Expert opinions

Experts from Email Geeks, Spamresource.com, and Wordtothewise.com agree that changing sending subdomains impacts email deliverability and necessitates a new warm-up process. Warming up the domain will help filters associate the domain and IP address to establish a sending reputation from scratch. It is advised to treat a new subdomain as a new sending source and introduce the switch at low volume, build it up gradually, and restrict sending to the best or engaged-only segments to prevent issues.

Key opinions

Warming Importance: Warming up a domain is vital when switching subdomains to allow filters to associate the domain and IP address.
Deliverability Impact: Changing subdomains impacts deliverability, even if the parent domain has a good reputation.
Separate Reputation: Subdomains need their own warm-up period, acting as a new sending source.
Warm-up required if new: If the subdomain is new, you will need to warm it up.

Key considerations

Gradual Introduction: Introduce the switch at a low volume and build it up gradually.
Engagement Focus: Restrict initial sending to only the best or engaged segments of your audience.
Treat as New: Treat a new subdomain as a completely new sending source requiring its own warm-up.

Expert view

Expert from Email Geeks explains the importance of warming up a domain and waiting for filters to associate the domain and IP address, particularly if the domain is not currently in use.

June 2023 - Email Geeks

Expert view

Expert from Wordtothewise.com, Laura Atkins, responds that sending email from a subdomain is a really useful strategy for separating types of mail, volume, and reputation. If the subdomain is new, you will need to warm it up.

November 2021 - Wordtothewise.com

Expert view

Expert from Email Geeks states domain warming does matter when switching domains, advising to introduce the switch at low volume and build it up gradually, also restricting sending to best only/engaged only for a bit to prevent issues.

June 2021 - Email Geeks

Expert view

Expert from Spamresource.com explains that subdomains need their own ramp-up (warm-up) period even if the main domain has a good reputation. They advise treating a new subdomain as a new sending source.

September 2022 - Spamresource.com

What the documentation says
4Technical articles

Documentation from Google, SendGrid, Mailjet, and Amazon SES consistently indicates that changing the sending subdomain impacts email deliverability and necessitates a new warm-up process. These sources emphasize that subdomains do not inherit the reputation of their parent domain and require establishing their own sending reputation. Without a proper warm-up, deliverability can be negatively impacted because ISPs need to learn to trust the new sending source. A domain warm-up process for new subdomains is crucial, and sudden increases in sending volume from a new source can damage sender reputation.

Key findings

No Reputation Inheritance: Subdomains do not inherit the reputation of their parent domain.
Warm-up Necessity: A new subdomain should be warmed up to establish its own sending reputation.
Deliverability Impact: Deliverability can be negatively impacted without a proper warm-up.
Trust Building: ISPs need to learn to trust the new sending source (subdomain).
Damage from Sudden Increases: Sudden increases in sending volume can damage sender reputation and deliverability.

Key considerations

Warm-up Process: Implement a domain warm-up process for new subdomains.
Gradual Volume Increase: Avoid sudden increases in sending volume when using a new subdomain.
Monitor Reputation: Monitor sender reputation closely during and after the warm-up process.
ISP Trust: Focus on building trust with ISPs by following best practices for email sending.

Technical article

Documentation from Mailjet advises a domain warm-up process for new subdomains. Mailjet documentation explains that while a subdomain is related to the primary domain, it still requires establishing a sending reputation to improve deliverability.

June 2024 - Mailjet

Technical article

Documentation from SendGrid emphasizes the importance of warming up new sending IPs and/or subdomains. It details that deliverability can be negatively impacted without a proper warm-up, as ISPs need to learn to trust the new sending source.

June 2021 - SendGrid

Technical article

Documentation from Google explains that subdomains do not inherit the reputation of their parent domain. Therefore, a new subdomain should be warmed up to establish its own sending reputation.

July 2024 - Google

Technical article

Documentation from Amazon SES specifies the importance of warming up new IP addresses or domains. Amazon SES explains that sudden increases in sending volume from a new source can damage sender reputation and deliverability.

October 2023 - Amazon

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