12 Ways to Improve your Email Deliverability & Inbox Placement in 2025
Master Email Deliverability & Inbox Placement with these Tips! Get insights into how we managed to do a 180° in this area at the end of the year 2024 - and secure your emails get seen!
Email Deliverability & Inbox Placement is the backbone of any successful Email Marketing Strategy. Whether you're crafting personalized campaigns, dynamic triggered emails, even the most engaging content is meaningless if it doesn’t land in your recipient’s inbox and in the correct folder/tab. In this post, we’ll explore actionable tips to improve your Email Deliverability & Inbox Placement, helping you reach your audience consistently through one of the most important channels in CRM.
With these Tips, you can achieve improved Reputation - like we did here with Brand #1:
And with Inbox Placement, go from this with our Brand #2:
To this:
—> Both examples in a span of 1 month!
Keyword Definition
Before we dive into the specific tips - it is fundamental that we define the keywords as we’ve seen that sometimes there is confusion around the specific meanings.
A.) Email Deliverability:
Email Deliverability is the ability of an email to be successfully delivered to a recipient's email server. It focuses on whether the email reaches the recipient's mailbox (in any folder, including spam or junk).
Email Deliverability we can “sub-categorize” into multiple areas - but the most important would be the “Reputation Category” —> In short, there is a “ Sender IP Reputation” and a “Sender (Sub)domain Reputation”, both play a critical role in your Email Deliverability Strategy, and therefore should be monitored closely - we will cover this part in one of our next blogposts, so stay tuned!
B.) Inbox Placement:
Inbox placement refers to where the delivered email ends up — whether it reaches the primary inbox, a sub-folder (like "Promotions" in Gmail), or the spam/junk folder.
If an email is delivered to the recipient’s server (= successfully achieved email deliverability), but it lands in spam/junk, it basically fails at Inbox Placement.
C.) Other used shortcuts / abbreviations:
ISP = Internet Service Provider —> A company that provides the email service, your email inbox provider (Gmail, Outlook/Microsoft, Verizon/Yahoo, etc.)
ESP = Email Service Provider —> The tool/software you use for sending emails (Mailchimp, MailerLite, Campaign Monitor, AWeber, Bloomreach, Klaviyo, Emarsys, etc.)
Introduction
The following tips are all elements we personally have experience with & implemented on our clients - so they are tested & proven to work. Though please keep in mind, every element here is a “specific lever” you can pull & observe what it does. There is no clear “manual” on what lever has which effects - it is like a video game, you need to figure it out while you go along. Ideally you play with multiple levers at the same time - this is all depending from your current Email Sending Behavior. A strategy to improve your specific Deliverability & Inbox Placement should be always crafted custom, based on how you perform in these areas.
I will also make sure to “score” these tips on a scale of 1-5 (1 meaning assumed least effectiveness, while 5 meaning assumed biggest effectiveness on Email Deliverability & Inbox Placement), so at least you have a small cheat code while you go along.
Oh - and before I forget, one more thing - these are Tips on “How To Improve Your Email Deliverability & Inbox Placement in 2025”. While going through this, we assume that your Technical Integration & Warm-up of your ESP is done, proven & reviewed. What we will therefore NOT be covering today are areas from the Integration & Authentication (things like: ESP selected, infrastructure setup, correct records generated & integrated - SPF/DKIM/DMARC/etc., database migration & compliance, warm-up successful, and so on.) We assume these steps were already taken at your end. If not - let us know & we can draft a post on that too!
So, with that being said - let’s dive into the #12 tips!
1.) Email List Hygiene (Score: 5/5)
One of the big ones. You should clean your email list & get rid of inactive subscribers. If you have this automated, even better!
When I tell this to clients I sometimes see the fear in their eyes - they are reporting to their boss on how their base is growing, not how it is shrinking (it might even be a KPI). It is therefore also very challenging to push through the implementation of this - but if you ask me, it truly does magic.
One of the big topics for ISPs is how relevant & engaging your content is to their customer base. If customers are not engaged (not opening/clicking), their generic filters deem your emails as “spam” and handle it accordingly. When you have a big chunk of your subscribers as inactive, this will have a big impact on your Inbox Placement. On the other hand, if you have a lot of active subscribers, it shows the ISP that your content is “consumed” and therefore it is handled accordingly. Ideally you should create a Segmentation of your subscribers based on their engagement levels - Bloomreach Engagement has a nice resource on this.
Another reason is that there is also something called “Spam Traps” - which are commonly used by ISPs to catch bad senders, but sometimes they target us - the good ones. If you hit these repeatedly, it shows the ISP that you have bad collection & cleaning practices with your subscriber base. In this specific case, you could be hitting a so called “Recycled / Expired Trap”, which are basically inboxes that once belonged to real humans, but after they have been abandoned (aka. nobody logged into the email for months to years), they are being “re-purposed” by the ISPs as a Trap - this can happen as soon as 6-12 months of no activity with the inbox!
I use the analogy from the dating world, I mean if you ask somebody on a date 5-10 times and they do not even respond (bonus points if you are kept on “unread”), one more try they surely will accept… Right? Right?!? ❌
Another way to argue here are truly the Metrics & KPIs. If you have 50% inactive subscribers (have not engaged with any email content, opened or clicked, for more than 365+ days for example), and you get rid of them - what will happen to your Open Rates, Click Rates, Click-Through-Rates, Conversion Rates in % from your base it is calculated from? It is an instant injection into the more meaningful KPIs than your Total Subscriber Base. More so, you are just wasting your resources & throwing money on a base that has simply no interest. True, email is cheap, but that does not mean you can be wasteful…
It’s just like in dating - let them go.
Side note in this part: We’re counting that you are removing hard bounces & spam complaints automatically from your base, as well as handle soft bounced addresses with care. Ideally your ESP would have this build-in. Bloomreach Engagement is great on this front - they automatically take care of these things for you in their tool & give you an understanding of the impact on your data - you do not need to do this yourself.
2.) Sent a Bulk Campaign to your Full Base at least once per 7 Days. Also, do not increase your Total Base from Bulk to Bulk by more than 22% without warming first (Score: 4/5)
With Emails, regular & consistent is the name of the game.
The underlying rule should be to sent min. 1x Bulk Campaign to your Full Base ideally at least once per 7 days (10-14 latest - but that is pushing it) - after you have been successfully warmed up of course.
What we have observed is, that sending a Bulk Campaign once per month is just not enough. Your IP & Subdomain reputation start to “cool down”, and that is also the case when you have automations running throughout the other days. After already 2 weeks reputation degrading can slowly start to kick-in.
Now you might be in a pickle - what if you have a smaller CRM Team and their Campaign Calendar says 1x Bulk per Month? We’ve worked with such a team - and the advise was to split the Bulk sent into ideally multiple weeks - then of course not reaching your Full Base with that Bulk, but reaching it throughout 3-4 weeks.
Bonus Advise: Take this opportunity to A/B Test the specific best day of the week & best time to sent the Bulk Campaign for your business! I know there is a ton of research on this topic available - but believe me when I say everyone’s customer base behaves differently, and you should not take research on the internet for granted - do you own!
Next, if your base would grow by more than 22% from one Bulk Campaign to another one, we would recommend to split the send into sending the first 11% with the initial base (= the 100%), the other 11% on the next day.
ISPs like consistency - if your base grows by a number/percentage that does not seem natural to them, their filters can start to raise red flags. It might be a sign of bad collection practices (“Where did you get that many subscribers from the blue?!”) - and also your IP/Subdomain Reputation might not be in a shape to sustain such an increase. We could go here into more detail, because usually at E3, we even look at bases with specific ISPs (Gmail, Microsoft, …) and if the base increases there above the threshold, we just make sure to warm-up that Domain only, as every ISP has their own rate limitations & reputation with you. Also, it might be that your customer base grew by 10% but Gmail by 50%. But - given that this is sometimes too advanced for clients without help - a generic rule of “+20%” is still OK to be sent, but anything above I would advise to split into multiple days.
Last point in this category is that if you start sending after a long period of inactivity (3+ months) - you cannot simply start where you left off. You need to, again, reestablish yourself as a “good & reputable” Sender. You are basically pushed back into the epoch of warm-up, if you ever wanted to time travel, this is pretty close to it if you ask me.
3.) Blacklist “soft bounces” temporarily with different timeframes, all based on their Reason/Error Code (Score: 4/5)
We’ve seen quite some positive results with this one.
Ideally your ESP would feed you back the specific “error codes” of soft bounces, and therefore allows you to handle each soft bounce differently. This is not the case with all ESPs, but it is very helpful, as a soft bounce can occur from very different reasons:
A soft email bounce is a type of temporary failure, and as the name suggests, means that your message cannot be delivered due to a temporary reason. Pretty vague, right?
Examples: server blocklisted, low user engagement, you sent too many messages too quickly, receiving ISP has connectivity issues, recipient’s inbox is full, …
If the ESP you work with gives you the codes of a soft bounce, you can research them online & handle each soft bounce differently - with different “temporary blacklisting timeframes”.
For example, we’ve had a client who had probably the majority (60% - 70%) of soft bounces because of “recipient’s inbox is full”. We also noticed, that usually when a customer was soft bounced because of a full inbox, it took them approximately a month to clean it up (if they did it at all). What we therefore did, was implement a solution where a “full inbox” would be blacklisted for up to 30 days, a “you sent too many messages too quickly” just for that one campaign, “ISP has connectivity issues” for 1 day and so on - based on reasoning & solutioning for soft codes. More critical is that we’ve observed even some soft bounces that could be handled as a hard bounce instantly (meaning, you should stop sending emails to them after the first bounce). Again, with an option to have the codes & error messages, you can blacklist a soft bounce indefinitely also.
At the end of the day, all of these tailor made customizations help you to be exposed to less soft bounces in a running 7-day period, and each soft bounce has negative effects on your reputation - so this allows you to minimize the exposure to soft bounces in general. If you combine it with the next tip on this list, it can get quite powerful!
4.) Double Opt-In is King, Email Validation is Queen & CAPTCHA is the Emperor (Score: 2/5 - as effects low, but generic Best Practice)
I know that you might not like DOI (= double opt-in), but given that it vets your customer before becoming a subscriber - aka. confirm the email is real and at the same time you already get an “active” subscriber who needed to click, and it automatically removes anyone who does not even open the very first email of yours, it’s just a very nice natural way of making sure your base is as clean as it can get. You wouldn’t believe how many people randomly subscribe without engaging with the first emails and not even with the Welcome, that is already a red flag that somebody will be a bad subscriber.
Bonus points if you can incorporate an Email Validation Service (here for Mailgun, here for Bloomreach) during your subscription process - this one is great, because it can catch invalid domains before you hit them & receive a hard bounce feedback (typical typo mistakes, “gnail.com”, “.con” and stuff like that). It also can get rid of subscribers that use “temporary email services” just to subscribe & get an incentive.
Anyway, using either or; or both is always an advantage.
CAPTCHA would be a mandatory recommendation - it offers basic protection against bots & harm done by others, you can be less exposed to attacks & issues.
Now to some quick and generic ✅ Do’s & ❌ Don'ts
5.) Don’t buy & scrape email addresses (Score: ∞)
Just no, please.
It might be also illegal in some jurisdictions, for example GDPR Article 4(11) could be brought up against you in this case. If we’re already on this point, be aware that based on Recital 32 for the Conditions for Consent states, that “silence, pre-ticked boxes or inactivity should not therefore constitute consent”. I am placing this just because it might be relevant to some readers.
6.) Avoid Spam Trigger Keywords (Score: 4/5)
ALL CAPS,
!!!!!! & over usage of special characters,
Over usage of “sale” terminology (Free, SALE, Promo, …)
Over usage of emojis “THIS DEAL IS 🔥🔥🔥🔥🔥”, etc.
—> Just be careful with the above. In addition, you can test your email body based on Spam Scores quick with mail-tester.com, Spam Checker by GlockApps or MailGenius.
7.) Incorporate Throttling into your Bulk sends (Score: 3/5)
Do not sent Bulk Campaigns all at once - depending on the size of your Total Base, throttle the send over 1-3 hrs. ideally. ISPs do not like bulk sends and hike spike volumes - they prefer a slower delivery. Basically, make sure you sent a specific batch of receivers every one/five/fifteen minutes.
Quick rule of thumb?
Up to 100K Base? —> 1 hrs. throttle
Between 100K - 300K Base? —> 2 hrs. throttle
300K+ Base? —> 3 hrs. throttle
8.) Balance Text-to-Image Ratios (Score: 3/5)
Maintaining an optimal proportion of text and images in your email content is critical as well. A common recommendation is a 60:40 ratio (60% text, 40% images) to ensure your email remains functional and deliverable, even if images fail to load. Image only emails can appear suspicious and be flagged by spam filters.
Make sure you are also sending email in “plain text” - there are still some humans around that have no smartphones, and plain text emails are useful for them. If your ESP can generate this automatically, even better for you.
9.) Make Unsubscriptions as easy & visible as you can, implement a “one-click unsubscribe” option as well (from Feb. 24 mandatory for Gmail/Yahoo)
Mandatory placement of an “unsubscription” link into the footer, also, implement a “list unsubscribe” functionality into the header of your emails.
With Bloomreach, it is as easy as to check a box in your settings and the link appears automatically.
10.) Personalize, Segment & Target (Score: 2/5)
You should align your messages with recipients preferences, behaviors, and needs - cater towards your audience in a more meaningful way. When emails are relevant and engaging, they generate higher open rates, click-through rates, and lower spam complaints - all of which signal to ISP that your emails are valuable/wanted.
However, the effects on Customer Experience & Email KPIs is probably more meaningful than the effects on Deliverability & Inbox Placement.
11.) Split your Marketing & Transactional emails into specific & standalone IPs & Subdomains (Score: 2/5, but generic best practice)
This is just generic & good advise, even though we’ve seen setups that work OK and are on a similar configuration (like same IPs). It is ultimately not advised - as any issues with your marketing emails can then affect transactional ones, and having deliverability issues in the transactional email category is one of the worst things to experience, it also overloads your Customer Support Teams immensely. Rather have it split, so that when there would be an issue with your marketing sends, it would not affect your transactional emails.
12.) Reduce Frequency to Inactive Subscribers (if low on reputation) (Score: 4/5)
The more engaged audiences you sent your emails to, the better your reputation becomes with ISPs. If you are struggling with bad reputation, it would make sense to reduce your email frequency to inactive subscribers. What would be even better is to not target them with standard Newsletters, but have specific Automations for this group to try to re-activate them. If you don’t succeed, just get rid of them & take away their consent.
How to Monitor all of this?
We wanted to cover this topic also here - but given the length of this blogpost, we decided to cover this part in one of our next posts in more detail.
The Secret Nobody Is Telling You About
The science behind Email Deliverability & Inbox Placement is… Well, unpredictable to say the least. Each ISP has their own algorithms, spam filters, generic rules, and so on. More so, these things are “ever changing” - meaning -updated as we go along with new innovations in this segment. Keep in mind, ISPs also do not officially communicate their filters, rules & algorithms in this area, making it even more difficult to investigate & consult on specific steps.
If you want to improve your Email Deliverability & Inbox placement, please also express patience - it is something you will need. You can expect to see improvements in this area in a span of 20-40 days (sometimes even sooner, but I rather not keep your hopes up). It is a long game, but definitely worth it.
Also, what works today might not work tomorrow - having said that, the above rules are quite “generic” and ever-green already for some years, so they should be hopefully applicable for the near future as well.
According to Statista, in 2023 there were 347.3 billion emails sent & received per day. Spam? Probably around 50% if not more. Amongst those scammers, AI generated content and so on. The ESPs try to do their best to protect their customer base & make the experience as comfortable as possible. Of course, sometimes they “miss” and deliver your email into spam - but now you should be well equipped to know how to fight back!
If you would need help implementing any of the above, review how you are doing, or draft a tailored Email Deliverability Strategy for you from all the various combinations of “levers” you can pull here, feel free to book a free 30-minute session to discuss how we can help you scale this mountain! ⛰️
May the odds be ever in your favor with the Emailing Gods. We’re confident, that with these tips you will be able to tip the scale even more in your own favor!