Diagnose delivery before increasing volume
Separate authentication failures, policy rejections, invalid recipients, and spam placement. Inspect provider responses and complaint trends before changing copy or buying another tool. A successful SMTP handoff does not establish that a message reached the inbox. Pause affected campaigns while fixing the cause, then resume gradually with verified, relevant recipients.
Every email that lands in the junk folder is a missed opportunity.
But while any cold outreach campaign is going to see some emails bounce or get marked as spam, there are plenty of steps you can take to hit more main inboxes.
Learn all about them in our guide to the latest tried-and-trusted email deliverability best practices.
21 Email Deliverability Best Practices You Need To Follow
1. Follow current sender requirements
The rules introduced in earlier years are already part of campaign setup. Check the requirements for the receiving service as well as your sending provider.
| Recipient service | Requirements to check |
|---|---|
| Personal Gmail | All senders need SPF or DKIM, valid forward and reverse DNS (PTR), TLS, and Postmaster Tools spam rates below 0.3%; Google recommends staying below 0.1%. At 5,000+ messages daily to personal Gmail accounts, also use both SPF and DKIM, a DMARC record, and From-domain alignment with SPF or DKIM. Marketing and subscribed messages need one-click unsubscribe and a visible body link. |
| Yahoo-hosted consumer mail | Yahoo requires SPF or DKIM for all senders, with both SPF and DKIM plus aligned DMARC for bulk senders. Bulk marketing mail needs easy unsubscribe, honored within two days. Yahoo does not publish Gmail’s numerical bulk threshold as its own rule. |
| Outlook.com consumer mail | Domains sending 5,000+ messages daily must pass SPF and DKIM and publish aligned DMARC at least at p=none. Authentication failures can be rejected with error 550 5.7.515. |
These consumer-service rules have a different scope from Google Workspace and Microsoft 365 business-mailbox sending limits. Authenticate every sending domain and monitor complaints and rejection codes regardless of volume.
2. Disable Open Tracking for Gmail
In 2024, Gmail began (yet another) experiment designed to crack down on unwanted emails.
It involves adding an ugly warning banner at the top of emails warning that the message contains hidden images:
This affects a somewhat important element of cold outreach: open rate tracking.
To track open rates without changing how an email looks, cold outreach platforms like QuickMail add an invisible image – typically measuring 1×1 pixel – somewhere in the email body. That way, we can tell when the email was opened (and, in some situations, also the reader’s IP address/location).
Clearly, this new banner warning increases the chances of cold email recipients reporting your messages as spam. Which is bad – remember, you have to keep spam complaints at <0.3%.
You can learn more about this whole situation in our guide: Gmail's New Banner Warning: What It Means for Open Tracking and Your Cold Outreach.
But, in a nutshell, QuickMail provides a simple solution – just disable open tracking for Gmail recipients only:
That way, you get around the Gmail issue while continuing to track opens for non-Gmail users.
While this means you get less tracking, it’s actually a smaller problem than you might think, with our data showing that Gmail “only” accounts for 27.5% of leads uploaded to QuickMail. That’s about 8.5% less than Outlook.
Alternatively, if you were already planning to add visible images to an email, you can take advantage of a QuickMail feature called Visible Image Tracking. It allows you to track opens with visible images – helping to prevent the email being flagged by Gmail.
3. Use Deliverability AI
QuickMail offers a ton of tools to overcome email deliverability issues, and one of our latest innovations is Deliverability AI.
With Deliverability AI, we automatically send your cold emails from the inbox with the highest deliverability score, saving you hours of individually analyzing inbox performance and manually swapping out under-performing senders.
This means your accounts cycle in and out of recovery as required, helping you maintain a healthy deliverability rate over the long term – without any tedious manual monitoring.
Clever, huh?
4. Never Use Your Own Domain
You are going to do things wrong and it’s too risky to use your primary professional domain.
You could use G Suite with a new domain.
When getting a new domain, you could be put into a spam list (fresh) automatically. It’s only for a higher risk of spam and it lasts about one month before you’re automatically de-listed. You can use lesser-known extensions (as opposed to .com) to avoid this, as not all extensions are monitored.
5. Never Use a Free Email Account for Cold Outreach
Free Gmail (@gmail.com) and Outlook accounts have better deliverability in general.
BUT, they are blocked quickly when a mistake is made, with no possibility to re-open them.
With professional accounts like G Suite, you have access to business support in case your account is blocked, and that usually can be resolved within 24 hours.
6. Choose a provider you can operate reliably
Compare Google Workspace and Microsoft 365 using your actual audience, administrative needs, authentication setup, and delivery results. Neither provider guarantees the best placement for every campaign.
Use Google’s current sending limits and Microsoft’s Exchange Online limits. Trial accounts and tenants can have different restrictions. Old advice to prepay a particular amount is not a reliable way to establish your current allowance.
Mailbox and tenant limits are ceilings, not recommended cold outreach volumes. Count follow-ups and ordinary business mail when planning sends, and reduce volume when the provider returns throttling or reputation errors.
7. Make Sure SPF and DKIM are Set for Your Domain
Because you’ll go straight to the junk folder if you don’t. Here are some shortcuts to help you out:
8. Check Your deliverability
Use services like spamtester.ai to determine your deliverability and sender score. Then look at how it can be improved by addressing all of their recommendations.
9. Warm Up Your Inbox
Use an email warm-up tool like Mailflow to warm up your inbox before and during campaigns.Â
Using a tool like Mailflow, your email account will automatically send emails to a network of real people inboxes talking to each other. Your emails will automatically be opened, and some of them will be replied to. This positive engagement will result in higher deliverability for your email campaigns.
Users have reported seeing a ~20% increase in open rates just from using this free tool.
10. Verify Your Email List Prior to Sending
It’s of utter importance to make sure the email addresses on your list won’t bounce. Google and other mail providers will block your account quickly. Bounce = spammer. So make sure all your emails are verified.
Never buy lists, and make sure you always use services like Neverbounce to clear your list first.
11. Avoid Similar Content
Similar email content gets flagged as spam. Use custom attributes to make sure you’re always sending unique, personalized content, and create a few different email variations (like A/B testing).
We’ve also created a solution to ensure you never have to send the same email twice: Reword with AI.
With Reword with AI, every email you send will be automatically rewritten. Our AI tool generates all-new relevant content based on the copy in any email step, rephrasing the emails sent while retaining the meaning of the original message.
This helps your sending activity look less spammy (and more personalized), helping you maintain a strong sender reputation and reducing your risk of potential deliverability issues
All QuickMail plans include monthly Reword with AI credits, up to 5,000 per month on our new agency plans.
Pricing: Compare current plans and limits. Confirm the billing term and allowances for your workflow.
12. Delay Message Sending
By default, QuickMail spaces out emails by 60 seconds.
You can increase that number by as much as you like – the higher the number, the less likely you are to be flagged as spam.
Alternatively add a random time variation between each email send so your activity looks less automated and more human.
13. Don’t Add Images in the First Email
Don’t add images in your first touch email if you can avoid it. Usually, the text on the first email is short. Adding an image has a bad text-to-image ratio, and spam filters don’t like that.
Tracking pixels (to determine open rate) are images. So to increase deliverability, you should consider disabling the tracking of opens in the first message.
Once follow-ups kick in, there will be enough text so that the ratio is not completely off.
14. Add No More than 1 Link Per Email (and Don’t Mask Links)
If you track links, make sure they’re not coming from a shortening service (e.g Bit.ly). Those are likely to be listed in spam lists already. Spammers use these link shortening techniques all the time, and you don’t want to be lumped in with the spammers.
Use description instead of URL. For example, if your link is www.mydomain.com, use “My Domain”… don’t put “www.mydomain.com,” as the tracking link will point to another address and services will often think it’s a phishing attack. Either write the URL without making a clickable link or disable click tracking in the first message.
15. Don’t Contact More Than 50 People/Day
If you do it right, you can get around a 20% reply rate.
No need to max out Gmail’s limit.
– It’s hard to find 2k valid emails that won’t bounce each day
– You don’t have the bandwidth to seriously engage with 400 replies anyway
Don’t go for quantity, as you’ll be punished in many ways. Try to nail it down with low volume first.
16. Avoid Unusual Bursts of Emails
It’s way better to send 50 emails each day than to send 250 emails one day a week.
Spam filters pay attention to things that are out of the ordinary. So to fly under the radar, have a continuous amount of emails sent daily rather than a one-time event that may be caught.
17. Only Send to Individuals
Always send to an individual email address, not groups such as marketing@, info@, sales@ … if you do, you’ll run the chance of getting flagged as a spammer.
18. Send to Business Emails, Not Personal Emails
Avoid @yahoo.com, @gmail.com, and other free types of emails, as they are more likely to be personal emails and not business emails. Personal emails addressed with business activities lead to greater spam complaints.
19. Don’t Sell on the First Email
The goal of cold emails is to engage in a conversation, not to get a sale from the first email. It’s best to sell only once you’ve created a relationship; not before.
People who try to sell right away get flagged as spam super fast, and future emails will end up in junk folders.
20. Don’t Repeat Yourself in a Follow-Up
Include the previous email for context, and provide a different call to action. Remember to always add new value with each follow-up email.
21. Type as if It Was Text Only
It’s not a beauty contest. Write cold emails like a human. No color, no bullet points, bold text, or custom fonts… resist the urge!
Improve Your Email Deliverability With QuickMail
As a mass email sender, the easiest way to hit more main inboxes is to use a cold outreach solution built around email deliverability.
Lots of platforms promise to prioritize deliverability. But only QuickMail includes all the tools you need to maintain high email deliverability at scale, like:
- Deliverability AI to automatically send from top-performing inboxes
- Reword with AI to ensure every email you send is unique
- Inclusive inbox warmup through MailFlow
Plus all the other email deliverability essentials (think blacklist monitoring, variable time delays between emails, Spintext, MX bounce protection, text-only messages, unsubscribe email headers, A/Z testing, maximum daily email limits, and more).
That’s why John Karsant, founder and CEO of LevelUp Leads, said:
“The number one thing that stuck out to me when I switched to Quickmail was the features around deliverability. Before QuickMail, I had to use other tools separately to check deliverability, so the fact that QuickMail had it built-in was a differentiator because so many other email services don’t have that.”
But don’t take his word for it – see for yourself by requesting your QuickMail agency demo.
Email Deliverability FAQs
What is email deliverability?
Email deliverability is the percentage of emails you send that land in a recipient’s inbox, rather than being blocked or marked as spam. It’s an essential way to measure how many of your messages are reaching your target audience.
Email delivery vs email deliverability: What’s the difference?
Email delivery and email deliverability are similar metrics, but they’re not identical:
- Email delivery rates track the percentage of emails that are successfully sent from the sender’s mail server to the recipient’s server.
- Email deliverability tracks whether a sent email lands in the recipient’s primary inbox (rather than the spam folder).
Why is email deliverability important?
Email deliverability is important because it speaks to the proportion of your outreach emails that actually reach their intended audience. If you have low email deliverability, a high percentage of recipients won’t see your emails – which means low opens and replies (and fewer leads).
What is a good email deliverability rate?
A good email deliverability rate is 95%+. If your deliverability rate is lower than this, it suggests you have one or more of the following problems:
- High bounce rate
- Low email engagement rates
- Poor domain reputation
How do you check email deliverability?
You can check email deliverability in QuickMail. Our key metrics track every lead activity back to the day the email was sent, which makes it easy for you to understand the impact of any campaign changes – including increases or decreases to your email deliverability.
