How long does IP warming usually take for 300,000 contacts?

Given a list of 300,000 contacts and a month of low sending volume, IP warming could take anywhere from 30 days to several months. The actual duration depends on factors like the list's engagement, your daily volume increases, and how quickly ISPs trust your sending patterns. Consistent monitoring of engagement and deliverability metrics is key to knowing when you can safely increase volume.

What kind of emails should I send during the IP warm-up process?

During the initial phases of IP warming, focus on sending emails that are highly anticipated and relevant to the recipient, leading to strong engagement. Transactional emails, such as order confirmations, shipping updates, or password resets, are ideal because they typically have high open and click rates. A well-crafted welcome series or introductory email (especially if the acquired company sent a 'goodbye' message) for engaged subscribers can also work very well.

What if my engagement rates drop during the warm-up?

If your engagement rates (opens, clicks) drop, or your bounce/complaint rates increase during warm-up, it's a critical warning sign. You should immediately slow down your sending volume or even pause for a day or two. Analyze your recent sends to identify any potential issues, such as unengaged segments or problematic content. Address the root cause before resuming your warm-up at a lower, safer volume. Checking your blocklist monitoring status is also important.

Should I warn the acquired contacts before sending emails?

Yes, it is highly recommended to inform the acquired contacts about the transition. Ideally, the acquired company should send a 'goodbye' email from their original domain, announcing the acquisition and letting subscribers know that your company will be taking over communications. Following this, your first email to them should be a clear, concise introduction from your domain, reminding them of the transition and setting expectations for future communications. This proactive approach minimizes confusion and reduces spam complaints.

How should I warm up IPs after acquiring a company with 300,000 contacts? - Sender reputation - Email deliverability - Knowledge base

Acquiring a company often comes with exciting opportunities, including a significant expansion of your contact list. However, integrating a large new audience, like 300,000 contacts, into your existing email program requires careful planning, especially when it comes to IP warming. Even if you've done some light IP warming previously, a month of lower sending volume means your IP's reputation might have cooled, requiring a refreshed approach.

The goal is to gradually re-establish a positive sender reputation with internet service providers (ISPs) and mailbox providers (MBPs) so your emails land in the inbox, not the spam folder. Rushing this process can lead to immediate deliverability issues, including emails being bounced, throttled, or even your IP address (and domain) getting added to an email blacklist (or blocklist).

Considering you peaked at 2,400 emails a month ago and have since been sending only in the hundreds for post-purchase communications, you need to treat this as a restart, or at least a significant step back, in your IP warming journey. The sudden jump to 300,000 contacts requires a highly strategic and cautious approach.

Assessing your current IP reputation and contact list

Before you send a single email to your new 300,000 contacts, you need to understand the current state of your IP's reputation and the quality of the acquired list. Your sending volume has significantly decreased from a peak of 2,400 to just hundreds daily for a month, which means your IP's active sending reputation has likely decayed.

A crucial first step is to assess the engagement history of these acquired contacts. Are they recently active? Do you have granular engagement data, such as opens and clicks, from their previous interactions? If the contacts haven't been mailed in a while or you lack recent engagement data, they could pose a significant risk.

Sending to an unengaged or stale list can lead to high bounce rates, spam complaints, and hitting spam traps, all of which severely damage your sender reputation and can lead to immediate IP or domain blacklisting (or blocklisting). Even with an engaged list, like a cat food subscription, a sudden, large influx of email can trigger unexpected volume filters at ISPs.

Assessing contact list quality

It's critical to determine the freshness and responsiveness of the acquired email addresses. If the prior company was sending regularly to these contacts and they were highly engaged, your warm-up will be smoother. If the list is older or engagement data is sparse, you'll need to be extra cautious.

Crafting your warm-up strategy

Given the month-long dip in volume, you should treat this as a new IP warming process, starting from your current daily sending volume (the hundreds). Do not jump back to the 2,400 daily peak from a month ago, let alone instantly to a fraction of 300,000. Gradually increasing your volume is the safest strategy to build trust with ISPs and avoid triggering spam filters. A good starting point for IP warm-up is to send small volumes of highly engaged emails, gradually increasing over time. MBPs and email providers recommend building sending reputation over time.

Segmenting your acquired list is paramount. Identify and prioritize the most engaged contacts first. These are the subscribers who have recently opened, clicked, or interacted with emails from the acquired company. Starting with this highly active segment provides strong positive engagement signals to ISPs, which is crucial during the initial warm-up phases.

The type of content you send during warm-up also matters. Transactional emails, such as purchase confirmations or shipping updates, are ideal because they have very high engagement rates. Welcome series emails to newly acquired subscribers can also work well, especially if the previous company sent a 'goodbye' email to prepare them for your communications. According to Rejoiner, transactional emails are best for warming an IP address.

Day	Volume Target	Focus List Segment
1-3	Hundreds (current daily volume) - 1,000	Most engaged (past 30 days)
4-7	1,000 - 5,000 (increase by ~25-30% daily)	Engaged (past 60-90 days), transactional
8-14	5,000 - 20,000 (continue ~25-30% daily increase)	Broader engaged segments, critical updates
15-30+	20,000 - 300,000+ (monitor closely)	Remaining active subscribers, marketing emails

Protecting your sender reputation

Throughout the warm-up process, constant monitoring of your email metrics is non-negotiable. Pay close attention to your open rates, click-through rates, bounce rates, and crucially, your complaint rates and unsubscribe rates. These metrics are direct indicators of how ISPs and your subscribers are perceiving your emails.

If you notice a sudden dip in engagement (opens/clicks) or a spike in bounces or complaints, it's a clear signal to slow down or even pause your sending volume increase. ISPs use these signals to determine your sender reputation, and a negative trend can quickly lead to throttling or blacklisting (or blocklisting). You can use a blocklist checker to actively monitor your IP for listing.

Clear communication with the newly acquired contacts is essential. Ensure the acquired company sends a goodbye email from their domain, explaining the transition to your company. Then, your first email to these contacts should be a clear, concise introduction that sets expectations. This helps minimize confusion and reduces the likelihood of complaints or users marking your emails as spam.

Risks of aggressive sending

Sending too many emails too quickly, especially to an unengaged portion of the acquired list, can lead to severe consequences for your deliverability. This can result in:

Blocked emails: Many ISPs will simply refuse your mail, leading to high bounce rates.
Blocklisting: Your IP or domain could be added to a public or private blacklist (or blocklist), making it difficult to reach any inbox.
Spam folder placement: Even if emails aren't blocked, they might consistently land in the spam folder, rendering your efforts useless.
Reputation damage: It takes a long time to recover a damaged sender reputation. Consistent negative sending patterns are hard to undo.

Advanced considerations and tools

Beyond just IP warming, consider if the acquired company used a different sending domain. If so, you'll need to warm up that domain in tandem with your IP, or potentially migrate those contacts to your existing, warmed domain. This can be complex, and a well-planned domain warm-up strategy is essential.

Ensure your email authentication protocols—SPF, DKIM, and DMARC—are correctly configured for your sending domain and IP. These standards prove to ISPs that your emails are legitimate and prevent spoofing. Regularly monitoring your DMARC reports can provide invaluable insights into your deliverability performance and identify potential issues during the warm-up.

Ultimately, successful IP warming and integration of a large contact list require patience and a commitment to best practices. Don't be afraid to adjust your sending volume based on real-time feedback from ISPs and your engagement metrics. It's a continuous process of building and maintaining trust with mailbox providers.

Views from the trenches

Best practices

Start from your current consistent daily sending volume and gradually increase it, rather than trying to match a past peak.

Segment the newly acquired list and prioritize sending to the most engaged contacts first to build positive sender reputation.

Utilize high-engagement emails like transactional messages or a specific welcome series during the initial warming phase.

Monitor key email metrics, including open rates, click-through rates, bounce rates, and complaint rates, daily.

Common pitfalls

Attempting to resume warming at a previously achieved peak volume after a significant drop in sending activity.

Sending to the entire acquired list too quickly, which can trigger spam traps and lead to immediate blacklisting (or blocklisting).

Failing to inform acquired contacts about the change in sender, causing confusion and increased spam complaints.

Ignoring dips in engagement metrics or spikes in complaints during the warm-up, leading to long-term deliverability issues.

Expert tips

A well-crafted introduction sequence for new subscribers can significantly improve engagement and reduce complaints.

The initial engagement of your warmest contacts will dictate how quickly you can scale your sending volume.

Even a highly engaged list, like subscribers to a cat food company, requires careful volume scaling to avoid 'unexpected volume' flags.

Consider warming up a new domain in parallel if the acquired company used a different sending domain.

Marketer view

Marketer from Email Geeks says to start from your current volumes and grow from there, emphasizing a gradual increase.

October 29, 2024 - Email Geeks

Marketer view

Marketer from Email Geeks says that if open and click rates remain high, you can grow by 30% a day, but slow down or pause if they drop.

October 29, 2024 - Email Geeks

Moving forward with confidence

Successfully integrating 300,000 contacts from an acquired company requires a strategic and patient IP warming approach. Since your IP's activity has been low for a month, it's best to restart your warming from your current, lower sending volume, rather than trying to resume at a previous peak.

Prioritize your most engaged contacts, use high-engagement content like transactional emails, and diligently monitor your email metrics. Clear communication with the new subscribers through an introductory sequence is also key. By taking these steps, you can smoothly integrate the new contacts while protecting your sender reputation and ensuring high deliverability.