What are the best practices for warming up established email addresses for sales reps reaching out to inbound opted-in leads?
Michael Ko
Co-founder & CEO, Suped
Published 25 Apr 2025
Updated 19 Aug 2025
7 min read
Warming up email addresses is a critical practice for maintaining good sender reputation and ensuring your messages land in the inbox, rather than the spam folder. When sales representatives are reaching out to inbound, opted-in leads, the dynamic is slightly different than cold outreach. These leads have already shown interest, which can positively impact engagement rates, but establishing a new sending volume from an existing, unused domain still requires a strategic approach.
The goal is to gradually introduce your sending activity to mailbox providers to build trust. Even with an established domain, if it hasn't been actively used for email outreach, it lacks recent sending history that mailbox providers can analyze. This history includes factors like bounce rates, spam complaints, engagement metrics (opens and clicks), and how consistently you send emails.
Understanding this nuance is key. We're not talking about warming up a new domain for cold contacts, but rather activating an established domain for a known, engaged audience. This generally makes the process smoother, but it still requires careful attention to detail to avoid triggering spam filters or getting your domain added to a blocklist (or blacklist).
Gradual volume ramp-up for established domains
Even with opted-in leads, starting with a gradual increase in sending volume is crucial. This helps mailbox providers like Microsoft understand your sending patterns and prevents them from flagging your sudden activity as suspicious. Think of it like building a credit score for your email address. You start small, prove your reliability, and then gradually expand your activities.
Begin by sending a small number of emails to your most engaged leads. These are the leads who have recently interacted with your brand, perhaps by filling out a form, downloading content, or visiting your website. Their expected high engagement (opens, clicks, replies) will send positive signals to mailbox providers. This initial phase sets a strong foundation for your sending reputation.
Start small: Begin with a low daily volume, perhaps 20-50 emails per sales rep per day. This initial volume is manageable and allows you to monitor performance closely.
Gradual increase: Increase the volume by a small percentage (e.g., 10-20%) each day or every few days. This slow and steady approach is key.
Consistency matters: Try to maintain a consistent sending schedule. Erratic sending patterns can raise red flags with spam filters.
Since you're using a sales enablement tool that sends directly through the inbox provider, the warming process is slightly less about IP warming and more about domain and email address reputation. However, the principles of gradual volume increase and positive engagement remain the same.
Personalization and engagement
Even with opted-in leads, personalizing your outreach is paramount. Generic, mass emails are more likely to be ignored or marked as spam, even by interested recipients. Sales reps should leverage the information gathered about these inbound leads to craft highly relevant messages. This means referencing their specific actions (e.g., downloading a whitepaper), their industry, or company-specific details. This will naturally increase engagement, which is a powerful signal for reputation.
Focus on content that provides value and encourages a response. This isn't just about making a sale, but about starting a conversation. Your initial emails should aim to answer potential questions, provide further helpful resources, or offer a brief call to discuss their needs. Avoid overly promotional language, which can trigger spam filters and disengage recipients. For more guidance on this, consider resources on sales follow-up best practices.
Inbound (Opted-in leads)
Audience: Individuals who have expressed interest in your product or service.
Expectation: Higher likelihood of engagement and lower spam complaints.
Content focus: Value-driven, personalized follow-ups that address their specific interest.
Cold (Unsolicited outreach)
Audience: Individuals with no prior engagement with your brand.
Expectation: Higher risk of low engagement, bounces, and spam reports.
Content focus: Introduction, compelling value proposition, and clear call to action.
The key distinction here is permission. Since these leads are opted-in, your focus shifts from building initial trust to nurturing an existing relationship. This context allows for a more direct, yet still personalized, approach compared to general cold outreach strategies.
Technical setup and monitoring
Even for established domains, ensuring your email authentication records are correctly set up is fundamental. SPF, DKIM, and DMARC are crucial for proving to mailbox providers that you are a legitimate sender and that your emails haven't been tampered with. These records help prevent spoofing and phishing attempts, which in turn protects your sender reputation.
A misconfigured SPF record, a missing DKIM signature, or a DMARC policy that's too restrictive without proper monitoring can lead to your emails being rejected or sent to spam, even for opted-in leads. Tools for DMARC monitoring can provide valuable insights into your email authentication status and identify any issues quickly.
Given that sales enablement tools often send emails directly through the inbox provider (like Gmail or Outlook), ensuring these fundamental DNS records are perfect is your primary technical control for good deliverability. A solid understanding of DMARC, SPF, and DKIM is invaluable.
Check your DNS records
Verify your SPF, DKIM, and DMARC records are correctly configured and aligned for all sending domains and subdomains. Misconfigurations can lead to emails being rejected or classified as spam, impacting your sender reputation.
One of the quickest ways to damage your email sending reputation (and trigger a blocklist) is to send to invalid or unengaged email addresses. Even with opted-in leads, lists can decay over time. Regularly cleaning your list by removing hard bounces, inactive subscribers, and known spam traps is essential. This proactive measure ensures that your engagement metrics remain high, sending positive signals to mailbox providers.
Monitor your deliverability metrics closely. Pay attention to open rates, click-through rates, reply rates, and especially bounce rates and spam complaint rates. A sudden spike in bounces or complaints indicates a problem that needs immediate attention. High bounce rates can quickly lead to your email addresses or even your entire domain being put on a blacklist (or blocklist).
Tools for blocklist monitoring are invaluable for staying on top of your reputation. If you find your domain or IP on a blacklist, it can severely impact your deliverability. Prompt action to address the underlying cause and request delisting is necessary. Maintaining a good reputation is an ongoing process, not a one-time setup.
Views from the trenches
Best practices
Start with very low daily sending volumes and gradually increase, even for opted-in leads.
Prioritize sending to your most engaged and recently active leads first to build positive sender reputation signals.
Ensure all email authentication records like SPF, DKIM, and DMARC are properly configured and aligned.
Regularly clean your email list to remove inactive or invalid addresses, reducing bounce rates and spam traps.
Personalize emails to reflect specific lead interactions, fostering higher engagement and fewer spam complaints.
Common pitfalls
Attempting to send high volumes of emails immediately after a long period of inactivity from an established domain.
Neglecting to monitor email deliverability metrics such as bounce rates and spam complaint rates.
Sending generic or overly promotional emails, even to opted-in leads, which can still trigger spam filters.
Failing to implement or correctly configure SPF, DKIM, and DMARC, leading to authentication failures.
Ignoring list hygiene and continuing to send to unengaged or invalid addresses.
Expert tips
Use internal email addresses to kick off initial sending before reaching out to external leads.
Subscribe to relevant newsletters from well-known brands to learn from their sending patterns.
Focus on two-way conversations and concise messaging to encourage replies and engagement.
Be strategic about when and how often sales reps follow up with leads.
Leverage sales enablement tools that integrate directly with inbox providers for seamless sending.
Expert view
Expert from Email Geeks says that warmup introduces recipient mail filters to your mail stream and the type of mail you're sending, emphasizing it's not worth doing if the mail is unwanted.
2024-06-13 - Email Geeks
Expert view
Expert from Email Geeks says that for the volumes being discussed (up to 1000 daily limit), there won't be much of a reputation either way, so you can just start using the established domain.
2024-06-14 - Email Geeks
Maintaining effective outreach
Warming up established email addresses for sales reps reaching out to inbound, opted-in leads is less about overcoming initial skepticism and more about building a healthy sending pattern and maintaining technical compliance. While the leads are already warm, the email infrastructure may not be.
By combining a gradual volume ramp-up, highly personalized and engaging content, robust email authentication, and diligent monitoring of your deliverability metrics, sales reps can effectively reach their valuable leads without falling into spam folders. This comprehensive approach ensures that the trust your leads have already placed in you extends to your email communications.
Gmail or 
Outlook), ensuring these fundamental DNS records are perfect is your primary technical control for good deliverability. A solid understanding of DMARC, SPF, and DKIM is invaluable.
