Many businesses are noticing that their emails land in spam more often or aren't delivered at all. The cause is stricter checks by providers like Gmail. Today, deliverability requires clean technology, clear sender structures and recipient behavior that makes sense. This article puts the developments in context and shows pragmatic solutions.
Email deliverability matters more than ever
Email is one of the most reliable means of communication on the internet. At the same time, it's one of the most suspicious. Nearly everything we communicate about customer service, invoices, offers or ticket updates happens over email.
Still, a small change behind the scenes is often enough to make email feel unreliable. That's exactly what many teams are noticing right now. You hear more and more comments like “More and more messages are landing in spam” or “Emails aren't arriving at all anymore”.
This phenomenon is the result of two parallel developments, not just a single problem. First, the leading email providers check the technical basics much more strictly today than in the past. Second, they scrutinize content and recipient behavior more aggressively. The message is clear: in 2025/2026, email deliverability is an engineering topic.
Why spam feels different today than it used to
Many people think of spam as a folder in their inbox. Technically, however, a provider makes two completely different decisions.
Stage 1: Is the email accepted at all?
Think of a mail carrier at the front door. If the technology isn't right, Gmail can reject a message as soon as delivery is attempted.
Stage 2: If the email is accepted, where does it land?
In the inbox or in the spam folder.
In the past, the first decision was more or less ignored. The email was accepted and sorted into spam if necessary. Today, exactly this first stage is handled much more strictly.
That matters because it changes how the problem feels for senders. Instead of “worse placement”, it's now: “The email doesn't arrive at all”.
This development is key to understanding the current situation.
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The Gmail enforcement phase
Google already introduced new requirements for email senders in 2024, especially for so-called bulk senders, meaning senders with larger sending volumes.
The significant difference since November 2025 is enforcement. Gmail now checks these requirements much more strictly.
What this means in practice
If you don't meet the minimum technical requirements, you get worse inbox placement or are rejected completely.
Gmail distinguishes between two cases:
Temporary rejection
The message isn't accepted but can be delivered again later. It's delayed.
Permanent rejection
The message is turned away and won't arrive until the underlying problem is fixed.
This tightening increasingly replaces the old pattern of “it just lands in spam” with “it's not accepted at all”.
One important limitation
These rules apply to emails sent to personal Gmail inboxes. Internal communication within Google Workspace business domains isn't affected.
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What is a bulk sender?
The term “bulk sender” sounds like newsletter campaigns. In practice, though, you can get classified as one much faster.
Service communication, more extensive onboarding sequences or a mix of transactional and marketing-style emails can be enough.
Roughly speaking, Gmail looks at this criterion
If you get close to 5,000 emails to personal Gmail accounts within 24 hours, you can be classified as a bulk sender.
Gmail doesn't count individual sender addresses but the parent domain. If you send from main-domain.de and promotions.main-domain.de, for example, they can be assessed together.
Also important
This classification isn't a penalty. It's a categorization. Once you're considered a bulk sender, you're treated as one permanently and assessed more strictly.
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The technical foundation of deliverability
Three terms come up in every discussion about deliverability: SPF, DKIM and DMARC. They look complicated, but the basic principle is easy to understand. Think of an email like a classic letter:
The envelope shows a sender
The letter is dropped off at a post office
The recipient has to decide whether the sender is genuine and trustworthy.
SPF
SPF is an allowlist in DNS. You define which servers are authorized to send emails on behalf of your domain at all. If someone sends on behalf of your domain through a server that isn't on this allowlist, it looks like sender spoofing.
DKIM
DKIM is a digital signature. It confirms that the content of the email wasn't altered in transit and that it really comes from an authorized system. If SPF says “this server may send”, DKIM says “this email is genuine and unaltered”.
DMARC
DMARC is the rulebook. You define what should happen if SPF or DKIM fail. The benefit is twofold:
Protection against misuse of your domain
More consistent assessment by email providers
Alignment
The often overlooked detail “alignment” means that the domain the recipient sees matches the domain that's technically verified. Put simply: the name on the doorbell has to match the ID card.
It's possible for SPF and DKIM to pass but refer to a different domain than the visible sender address. In that case, the email counts as not aligned and fails DMARC.
Gmail also expects further technical basics
Encrypted transmission via TLS
Clean reverse DNS records
A formally correct email structure
These points are requirements, not optimizations.
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Why emails can land in spam despite perfect technology
Once an email passes all technical checks, the second stage of assessment begins: content, patterns and behavior. Gmail then no longer asks “Is this email allowed in?” but “Do recipients really want this email?”.
Three factors are especially decisive here:
Spam complaints
When recipients actively click “Report spam”, it's one of the strongest negative signals. Even low complaint rates can severely hurt deliverability.
Unsubscribing
For marketing emails, Gmail expects simple one-click unsubscribe. If it's missing or cumbersome, users click “Spam” instead of “Unsubscribe” more often.
Engagement
Opening, replying or deleting right away. Replies are a strong positive signal. Deleting unread or ignoring has a negative effect over time. That's why replies within existing conversations often get through better than first-contact emails. It's statistics, not magic.
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Why customer service emails are an easy target
Service systems automate email processing. That's exactly what makes things more complicated. Service messages often contain long email histories, lots of links, changing subject lines, attachments and recurring text snippets.
On top of that come technical metadata that are invisible to recipients but still factor into the assessment. Often it's not the big mistakes but the small things that add up and cause problems.
Rather than simply switching filters off, it makes more sense to have transparency about detected spam, easy “Not spam” corrections and continuous optimization based on real misclassifications.
See how ZYBR filters out spam and prepares replies with order and shipping status, using your own inbox: try ZYBR with your own customer emails.
A pragmatic path to better deliverability
Deliverability works a lot like fitness. A few basics have the biggest effect.
Get the technical foundation right. Keep SPF lean, align DKIM correctly and run DMARC at least in monitoring mode.
Treat marketing communication and customer service communication separately. Marketing tends to generate complaints, while customer service often generates replies. Separate domains or subdomains protect your reputation.
Tone down your content thoughtfully. Leaner HTML, fewer links, no unnecessary attachments. Actively encouraging replies is key.
Monitoring beats guessing. Google Postmaster Tools provide precise data. Checking spam folders in webmail adds clarity. Making corrections should be easy.
Conclusion
Gmail is making the inbox stricter, but also more consistent. The tightening at the end of 2025 is inconvenient but understandable. Today, even small configuration errors can cause real delivery problems.
Deliverability can be improved for good if you align SPF, DKIM and DMARC cleanly, separate marketing from customer service and take recipient behavior seriously. Email remains an essential channel, but in 2025, what “somehow” worked for years will stop working.
Service communication can be improved considerably by platforms like ZYBR that structure it cleanly on a technical level and make it transparent to analyze. That way, deliverability isn't left to chance but managed systematically.
Robin Wehner, Co-founder and Managing Director
Robin builds the AI behind ZYBR and thinks every system through, from the first draft to the finished reply. He spots edge cases before they happen. If something isn't right, it doesn't go live.
