Why do new sender email addresses experience lower rates and what can be done about it?
Michael Ko
Co-founder & CEO, Suped
Published 4 Jul 2025
Updated 18 Aug 2025
7 min read
It can be perplexing when you introduce a new sender email address, even on an established and healthy domain, only to see its performance dip. You've done everything right: you're sending to engaged contacts, your domain's reputation is solid, and spam rates are low, yet this new address struggles to reach the inbox or achieve expected engagement levels. This scenario is more common than many email marketers realize.
The core of the issue lies in how mailbox providers, like Google and Yahoo, assess sender trustworthiness. While your domain may have a pristine history, a specific email address within that domain is seen as a new entity by their filters. It lacks the sending history and user interaction data that an established address has accumulated.
This leads to what we can describe as a skepticism phase. Mailbox providers initially rate limit messages from new sender addresses and monitor recipient reactions closely. They want to understand if these new messages are genuinely desired by recipients or if they are unwanted, potentially spam, or even phishing attempts.
The challenge is that this skepticism can manifest as emails landing in spam folders or the promotions tab, leading to lower engagement metrics like open and click-through rates. This guide will explore why this happens and what practical steps you can take to build the necessary reputation for your new sender email addresses.
The challenge of a new identity
Even when your domain reputation is strong, a new sender email address within that domain is treated as a distinct entity by email filters. This is because mailbox providers analyze behavior at various levels, including IP, domain, and individual sender address. A lack of historical sending data from the specific new address triggers caution.
This initial caution often results in what is sometimes perceived as suppression. It is not an outright block, but rather a cautious approach where emails might be placed into less prominent folders, such as spam or promotions, until enough positive signals are gathered. This helps mailbox providers differentiate legitimate new senders from those with malicious intent.
The rationale behind this deep-level scrutiny is the rise of automated sending and warming services. To combat spam and ensure a clean inbox experience for their users, mailbox providers have extended their behavioral analysis beyond just the domain and IP to include the individual sender address's patterns. This means that a new sender name or address needs to build its own reputation, even if it's operating on a well-regarded domain.
Understanding the problem
Lack of history: New sender addresses have no prior engagement data for inbox providers to analyze.
Default skepticism: All new sending entities, including addresses, are viewed with caution to prevent spam.
Individual reputation: Reputation is now assessed at a granular level, even for individual sender addresses.
Building trust with senders and recipients
The primary strategy to overcome this initial skepticism is to warm up your new sender address. This involves gradually increasing your sending volume and ensuring high engagement from recipients. Think of it as building a positive behavioral history for that specific address.
During the warm-up phase, prioritize sending highly engaging content to your most active subscribers. Transactional emails, welcome sequences, or other messages that recipients are likely to open, click, or even move from spam to their inbox are excellent choices. These positive interactions signal to mailbox providers that the new address is legitimate and valued by recipients.
Consistency is key. Regular sending, even at lower volumes initially, is better than sporadic bursts. This helps mailbox providers (MBPs) gather enough data on the sending patterns and recipient reactions associated with that particular email address. Over time, as positive signals accumulate, the skepticism will decrease, and your inbox placement rates will improve.
Bad practices
Sudden volume: Sending large volumes from a new address immediately.
Low engagement: Sending to unengaged lists, leading to low opens and high complaints.
Ignoring metrics: Not monitoring open rates, spam complaints, and bounces.
No authentication: Failing to set up SPF, DKIM, and DMARC for the sending domain.
Beyond warming up, foundational technical elements are critical. Ensure that your domain has strong email authentication protocols in place: SPF, DKIM, and DMARC. These protocols verify that your emails are legitimately coming from your domain, which is a non-negotiable trust signal for mailbox providers.
Another crucial aspect is maintaining excellent list hygiene. High bounce rates and spam complaints, even from a new sender address, can quickly land you on a blocklist (or blacklist), which significantly damages your sender reputation. Regularly cleaning your email list to remove invalid or unengaged addresses helps maintain low bounce rates and high engagement, which is vital for new addresses.
I find that continuous monitoring of your email deliverability metrics is essential. Use tools like Google Postmaster Tools and your Email Service Provider's (ESP) analytics to track your open rates, bounce rates, and spam complaint rates specifically for the new sender address. This data provides insights into how mailbox providers are perceiving your emails and allows for quick adjustments if issues arise. If you notice a sudden drop in open rates, for example, it could indicate a problem with the new address's standing.
The skepticism applied to new sender addresses is a direct result of ongoing efforts by mailbox providers to reduce spam and improve the user experience. They don't outright suppress emails, but they do exercise extreme caution with new sending identities until a positive pattern of behavior is established.
This means that even if your domain has a low spam rate and high reputation, a new sender email address within that domain needs to build its own independent history of positive engagement. It takes a bit of consistent volume and positive user interaction for mailbox providers to categorize where emails from that specific {username}@ should primarily land.
Patience and strategic warming are key. Once you've sent consistently from that new username for a week or so, and mailbox providers have enough data from user reactions (like opens, replies, or moving from spam), the deliverability rates for that specific sender address will typically stabilize and improve. This is why a methodical warm-up plan is essential for any new sending identity.
Views from the trenches
Best practices
Start with very small volumes to highly engaged subscribers.
Use transactional emails or welcome series to establish trust.
Monitor deliverability metrics daily for the new address.
Ensure all email authentication records (SPF, DKIM, DMARC) are configured correctly.
Actively encourage subscribers to add your new sender address to their address book.
Common pitfalls
Sending large blast campaigns from a brand new sender address.
Not monitoring spam complaint rates for the new address.
Ignoring soft bounces, which can indicate initial filter issues.
Failing to clean your list, which can lead to spam trap hits.
Switching sender addresses frequently without proper warm-up.
Expert tips
Focus on messages users expect and will engage with positively.
Transactional emails are excellent for rapid positive signal generation.
Even well-known domains need to warm up new individual sender addresses.
Skepticism from ISPs has extended to the individual address level.
Sometimes lower open rates are due to pixel pre-fetching, not outright suppression.
Expert view
Expert from Email Geeks says inbox providers do not outright suppress emails from new sender addresses, but they do exhibit extreme skepticism towards them.
2024-02-12 - Email Geeks
Expert view
Expert from Email Geeks says filters use a similar methodology for testing new messages, regardless of whether it is a new address, content, IP, domain, or DKIM signing domain, by rate limiting and observing user reactions.
2024-02-12 - Email Geeks
Achieving deliverability success with new senders
Navigating the initial challenges with new sender email addresses requires understanding that mailbox providers prioritize user experience and security above all else. Their skepticism, while frustrating, is a necessary defense against unwanted email. By approaching new sender addresses with a strategic warm-up, a focus on engagement, and robust technical foundations, you can overcome these hurdles.
Remember, the goal is to consistently send emails that recipients want and expect. This positive feedback loop is what builds a strong sender reputation, not just at the domain level, but for each individual sending identity. It's a marathon, not a sprint, but the payoff is consistent inbox placement and improved email marketing performance.
By diligently following these practices, you will ensure that your new sender email addresses earn the trust required to reach your audience effectively. This commitment to best practices will help you avoid blocklists and achieve optimal deliverability over the long term, securing your email program's success.
