Summary
Using the same domain or IP address for cold and warm email campaigns significantly risks sender reputation and deliverability. Poor cold email practices, such as sending to unverified lists, ignoring unsubscribe requests, generating spam complaints, or failing to adhere to anti-spam policies, can lead ISPs and mailbox providers to flag the domain/IP as a source of spam. This results in legitimate, 'warm' emails being blocked, sent to the spam folder, or even resulting in blacklisting. While subdomains offer limited protection, complete separation via different domains and IP addresses is the recommended best practice to protect the primary domain's reputation. Addressing deliverability issues requires stopping the harmful cold email practices and actively rebuilding the sender reputation. Monitoring engagement, maintaining clean lists, and adhering to email marketing best practices are also crucial.
Key findings
- Reputation Degradation: Cold email activities can severely damage sender reputation, leading to deliverability problems for all emails from the domain/IP.
- Shared Infrastructure Risks: Using the same infrastructure (domain/IP) for cold and warm emails creates a significant risk to the deliverability of legitimate emails.
- Limited Subdomain Protection: Separating by subdomain provides limited protection; top-level domain reputation remains vulnerable.
- Domain/IP Separation is Key: Using separate domains and IP addresses for cold emails is the most effective way to protect the primary domain's reputation.
- Complaint Sensitivity: High volumes of spam complaints trigger filtering and blocking.
Key considerations
- Separate Cold Email Infrastructure: Prioritize using a distinct domain and IP address for cold email campaigns.
- Monitor Engagement Metrics: Actively monitor open rates, click-through rates, bounce rates, and spam complaints for cold email campaigns.
- Practice List Hygiene: Maintain a clean and verified email list by removing invalid addresses and honoring unsubscribe requests.
- Comply with Anti-Spam Laws: Ensure full compliance with anti-spam laws and regulations like CAN-SPAM, GDPR, and others.
- Rebuild Sender Reputation: Once cold email issues are resolved, actively rebuild the sender reputation of the primary domain using best practices.
- Train Sales Teams: Educate sales teams on proper email practices and the importance of protecting the brand's sender reputation. Avoid using the primary company website or domain in cold email messaging.
What email marketers say
8 marketer opinions
Sending cold emails using the same domain or IP address as your 'warm' emails can significantly harm your sender reputation and deliverability. Poor cold email practices, such as sending to unverified lists, ignoring unsubscribe requests, or generating spam complaints, can lead ISPs to flag your domain as a source of spam. This results in your legitimate emails being blocked or sent to the spam folder. While separating streams by subdomain offers limited protection, using entirely separate domains and IP addresses is recommended to avoid damaging your primary domain's reputation.
Key opinions
- Reputation Damage: Cold emails can damage sender reputation due to low engagement, spam complaints, and poor list hygiene.
- Deliverability Issues: Damaged reputation leads to 'warm' emails being blocked or sent to spam.
- Subdomain Limitations: Separating by subdomain provides limited protection; top-level domain reputation is affected.
- Domain/IP Separation: Using separate domains and IPs for cold emails is a recommended best practice.
Key considerations
- Monitor Engagement: Track open rates, click-through rates, and spam complaints for cold email campaigns.
- List Hygiene: Maintain a clean and verified email list for cold outreach.
- Separate Infrastructure: Consider using a separate domain and IP address for cold emails to protect your primary domain's reputation.
- Compliance: Adhere to anti-spam laws and best practices, including CAN-SPAM and GDPR.
Marketer view
Email marketer from Sendinblue Blog explains that using the same domain for cold and warm emails can damage your sender reputation if your cold emails have low engagement (opens, clicks). This can lead to your warm emails being marked as spam.
27 May 2021 - Sendinblue Blog
Marketer view
Email marketer from Email Marketing Forum explains that if you're blasting out cold emails and people are marking them as spam, that's going to hurt your overall domain reputation, no matter how 'warm' your other emails are supposed to be.
27 Jul 2024 - Email Marketing Forum
What the experts say
4 expert opinions
Cold email practices can severely impact the deliverability of legitimate 'warm' emails if they share the same domain or IP address. Spam complaints from cold emails can degrade sender reputation, leading to all emails from that domain going to spam. The best practice is to completely separate cold email activities onto a different domain and IP, and to avoid mentioning the primary domain in cold email communications. Fixing reputation requires stopping the problematic cold email practices.
Key opinions
- Reputation Degradation: Cold email can degrade domain reputation, causing all mail (including 'warm' mail) to go to spam.
- Shared Infrastructure Risks: Using the same domain and IP for cold and warm email compromises deliverability for both.
- Domain/IP Separation Essential: Separating cold email onto a different domain and IP address is the recommended practice.
- Stopping Cold Email Problem: Reputation fixes are ineffective without first stopping the problematic cold email practices.
Key considerations
- Inbox Testing: Conduct inbox testing to assess the impact of cold email on deliverability.
- Google Postmaster Tools: Use Google Postmaster Tools to monitor domain reputation for consumer domains.
- Sales Training: Train sales teams to avoid mentioning the primary domain in cold email communications.
- Reputation Rebuilding: After separating infrastructure, focus on rebuilding the reputation of the opt-in email program.
Expert view
Expert from Spam Resource explains that if cold emails generate spam complaints, even legitimate 'warm' emails sent from the same infrastructure (domain/IP) will suffer deliverability issues, potentially landing in spam folders or being blocked outright.
19 Jun 2021 - Spam Resource
Expert view
Expert from Word to the Wise explains using a separate domain and IP address for cold email is the best practice to avoid damaging the reputation of your primary domain used for legitimate email. Shared infrastructure risks deliverability for both streams.
20 Feb 2022 - Word to the Wise
What the documentation says
5 technical articles
Sending unsolicited emails, including cold emails violating anti-spam policies, negatively impacts sender reputation and deliverability. This can lead to emails being marked as spam, blocked, or IP/domain blacklisting, hindering the ability to send legitimate emails. High complaint volumes significantly contribute to filtering and blocking based on reputation. Adhering to best practices, obtaining consent, and avoiding spam-like content are crucial for maintaining a positive sender reputation.
Key findings
- Reputation Impact: Unwanted emails damage domain and IP reputation.
- Deliverability Issues: Poor reputation leads to spam filtering, blocking, and rejection of emails.
- Blacklisting Risk: Spam practices can cause IP/domain blacklisting.
- Complaint Sensitivity: High complaint volumes trigger filtering and blocking.
Key considerations
- Consent: Obtain proper consent before sending emails.
- Anti-Spam Policies: Adhere to anti-spam policies and regulations.
- Content Quality: Avoid spam-like content.
- Best Practices: Follow email marketing best practices to maintain a positive reputation.
Technical article
Documentation from Microsoft 365 documentation explains that sending unsolicited commercial email (spam) can lead to IP address and domain blacklisting, negatively affecting your ability to send legitimate email.
18 Oct 2021 - Microsoft 365 documentation
Technical article
Documentation from M3AAWG shares that volume of complaints impacts sending reputation. If people complain a lot they will filter or even block the mail based on volume and reputation.
30 Mar 2025 - M3AAWG
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