What Outlook, Gmail and Yahoo! Require to Keep Your Emails Out of Spam

Sending bulk emails – such as newsletters, promotions or notifications – is a common practice for many companies and organizations.

However, getting those messages into the inbox instead of the spam folder (junk mail) depends on meeting certain requirements set by the major email providers.

More than requirements, we could think of them as best practices that keep the world from filling up with spam.

Outlook (Microsoft’s email service, formerly known as Hotmail/Live) recently announced new conditions for high-volume senders, joining similar measures that Gmail and Yahoo! put in place starting in 2024.

Remember, too, that at Mailrelay, we help you set all of this up correctly to improve your results.

Outlook: new authentication requirements for bulk senders

Outlook.com (which covers @outlook.com, @hotmail.com and @live.com addresses, among others) is tightening its policies to protect users from spam and identity spoofing.

Starting in May 2025, domains that send more than 5,000 emails a day will be required to meet certain authentication measures.

This means that if your organization sends email in high volumes, Outlook will require you to set up security protocols for your emails, specifically SPF, DKIM and DMARC:

· SPF (Sender Policy Framework):

It’s a record in your domain’s DNS that lists which servers or IP addresses are authorized to send emails on your behalf.

Outlook will require the SPF to “match” and approve the message for your sender domain.

In other words, the server you send the email from must be included in your SPF record; otherwise, the email won’t pass this check.

· DKIM (DomainKeys Identified Mail):

It’s a system that adds a digital signature to every email you send.

Only the legitimate domain holds the key to generate that signature.

Outlook now requires DKIM to be set up and the signature to be valid on bulk messages.

This ensures the integrity of the message and confirms it hasn’t been altered along the way.

· DMARC (Domain-based Message Authentication, Reporting and Conformance):

It’s a policy you publish on your domain to specify how emails that fail SPF/DKIM should be handled.

Outlook will require at least a DMARC policy set to “p=none” (monitoring only), correctly configured and aligned with your domain.

Alignment means that the domain in the “From” field (the one the recipient sees) must match the domain authenticated by SPF or DKIM.

This prevents anyone from sending emails pretending to be your address.

· What happens if you don’t meet these requirements?

Microsoft announced that it will start routing non-compliant messages to the junk (spam) folder.

In other words, if your domain sends many emails without proper SPF, DKIM, or DMARC, those emails will land in the Junk folder on Outlook.com instead of the inbox.

This measure will begin just after May 5, 2025, giving senders time to adapt.

Later, on a date yet to be announced, Outlook may start rejecting (blocking) those emails entirely if the problem persists.

In short, to avoid Outlook sending your messages to spam, you must authenticate your email with these protocols as soon as possible.

· Beyond technical authentication, Outlook strongly recommends following good hygiene practices for bulk sending:

• Valid sender address: make sure the email shown as the sender (the “From:” or the “Reply-To:” if different) is valid and working. It must belong to your real domain and be able to receive replies. In practice, this means not using nonexistent “no-reply” addresses or domains you don’t control. An authentic sender inspires more trust.
• Working unsubscribe link: if you send newsletters or promotions, always include an easy, visible way to unsubscribe with a single click. This lets anyone who no longer wants to receive your emails say so quickly. Outlook stresses that the link must work properly and be clearly visible.
• List hygiene and bounce management: review your recipient list regularly and remove invalid or inactive addresses. When you send to lots of addresses that bounce (don’t exist) or to people who don’t remember subscribing, spam complaints go up. Keeping your list clean reduces wasted messages and user complaints.
• Transparent sending practices: avoid misleading headers or subject lines. Be clear in the subject line about the content of the email, and make sure the recipient has consented to receive it. Basically, don’t send bulk emails to people who didn’t ask for them, and don’t try to trick people with fake subject lines – that only gets your message marked as junk.

Outlook states that it reserves the right to filter or block senders who don’t follow these measures, especially if they fail authentication or engage in serious bad practices.

As a result, what should senders do? Review their domain configuration now.

Microsoft advises senders to “prepare now”: audit your DNS records to check that SPF, DKIM and DMARC are correctly set up and working.

Gmail: strong authentication, one-click unsubscribe, and spam control

Gmail, Google’s email service, has been fighting spam with smart filters for years, but since 2024 it has gone a step further by setting clear rules for high-volume senders.

Google announced that, to keep Gmail inboxes safe and free of junk mail, it would impose new requirements on “bulk senders”.

Who counts as a bulk sender? Anyone who sends more than 5,000 messages a day to Gmail accounts.

If your domain fits that category, pay attention to what Gmail requires to keep your emails out of the spam folder:

· Authenticate outgoing emails:

Gmail now requires large senders to strongly authenticate their emails following standard best practices.

In practice, this means having SPF and DKIM set up on your domain, as well as a DMARC record.

In fact, Google made it clear that high-volume senders must enable both SPF and DKIM (not just one of them), and also have a DMARC record even if it’s set to “none” (monitoring).

This prevents attackers from spoofing your address, as Gmail will verify the email actually comes from servers allowed and signed by your domain.

If your messages aren’t authenticated, Gmail is very likely to flag them as suspicious or simply not deliver them.

· Make it easy to unsubscribe with one click:

Google considers it essential that users can easily stop receiving unwanted emails.

That’s why it requires bulk senders to include a one-click unsubscribe option in every commercial email.

Additionally, unsubscribe requests must be processed quickly, within a maximum of two days.

In other words, if a Gmail user clicks “unsubscribe” in your email, you (or your mailing system) must remove them from the list within 48 hours and stop sending them messages.

Gmail bases these requirements on open standards that benefit all providers, so once they’re in place, it’s not just Gmail that benefits but any email recipient in general.

· Only send emails users expect (and want) to receive:

This point basically comes down to not spamming.

Gmail already filters a lot of unsolicited email automatically, but now it has gone a step further by setting a specific spam rate threshold that senders must stay under.

In practice, this means that if too many users report your messages as spam, you’ll have problems.

Google didn’t give the exact number in its announcement, but its sender guidelines state that you must keep your spam (complaint) rate below 0.3%.

In other words, out of every 1,000 emails you send, no more than 3 should be marked as spam by users.

If you go over that limit, Gmail may take action:

• For example, limit delivery
• Send more of your emails to the spam folder
• Or even block part of your traffic

In fact, Google said that starting in April 2024, it would begin rejecting a percentage of non-compliant emails under the new policies, increasing that percentage over time.

For example, if 25% of your messages are non-compliant (due to missing authentication or high complaint rates), Gmail may start bouncing some of those “problem” emails while letting compliant ones through.

This gradual enforcement approach is designed to push senders to improve without blocking all emails at once.

In short, Google has made mandatory practices that used to be simply good recommendations.

For senders, this means taking several specific actions if they want to maintain good deliverability with Gmail:

· Configure SPF, DKIM, and DMARC on your domain

This is the first step.

If you use an email marketing platform or provider, check with them that they’re signing your emails properly on your behalf.

Remember that DMARC only works if SPF/DKIM pass and the signing or server domain matches your address (alignment).

That’s why Gmail requires the domain shown in the “From:” field to align with SPF or DKIM.

· Keep your servers in order:

Gmail also notes that sending domains or IPs must have valid reverse DNS (PTR) records and use secure TLS connections.

We take care of this part at Mailrelay, so don’t worry.

· Include unsubscribe links and respect them:

Check your mass email templates and make sure to include a visible “unsubscribe” link.

Something like “If you no longer wish to receive this newsletter, click here” with a working link.

And most importantly: act when someone clicks.

Gmail will check that it’s actually easy to unsubscribe.

If many users mark your emails as “spam” simply because they couldn’t find how to unsubscribe, that hurts you.

· Maintain the quality of your email list:

Don’t send emails to people who didn’t ask for them.

Avoid buying contact lists (they usually include people who don’t even know you and will report you as spam).

Run re-confirmation campaigns if your list is old, to ensure people are still interested.

· Google considers these practices “basic email hygiene”

In fact, they noted that many legitimate senders were already following most of these requirements, but now they’ll be mandatory for everyone sending in large volumes.

The good news is that implementing these measures improves your email deliverability: Gmail notes that senders who authenticate properly and manage their lists carefully tend to have fewer bounces and more user trust, which means your messages will reach recipients more reliably.

In other words, it’s not just about “pleasing Gmail” — it genuinely strengthens your email marketing or communication efforts.

Yahoo!: authentication and respect for the user, the same mission against spam

Yahoo! Mail, which also includes AOL email and other email brands under Yahoo Inc., joined this initiative against spam almost at the same time as Google.

In the first quarter of 2024, they announced that all bulk senders would have to follow new rules to ensure “safer email with less spam”.

Yahoo’s three key requirements are practically the same three we’ve already seen:

· Authenticate email with secure standards:

Yahoo now requires high-volume senders to use SPF, DKIM, and DMARC on their emails.

Their position is that verifying the sender’s identity is crucial to prevent malicious third parties from impersonating you.

Like Gmail, Yahoo wants you to have, “at a minimum”, a DMARC record published and set up correctly, even if it’s in monitoring mode (p=none).

If your emails are not authenticated, they are much more likely to be blocked or marked as dangerous.

In short: Yahoo asks for exactly the same thing on this technical front as the other services – proving that your message is legitimate through these protections on your domain.

· Provide an easy unsubscribe option:

Yahoo emphasizes that its users should be able to stop receiving emails with a single click if they choose.

Although they have long promoted these practices voluntarily, they acknowledge adoption was low, so they decided to make it mandatory.

Specifically, Yahoo requires support for the “one-click unsubscribe” standard and, very importantly, that senders honor the request within a maximum of two days.

This means the same as with Gmail: include the “unsubscribe” link in your emails and process unsubscribes almost immediately.

If a Yahoo/AOL user clicks “I don’t want this email anymore,” you must ensure they are removed from future campaigns within 48 hours.

Yahoo has even stated that the unsubscribe feature must be completely reliable and hassle-free for the user (without asking for unnecessary extra steps).

· Only send to those who want your emails:

Yahoo’s (and everyone’s) core philosophy is that the best spam is the one that’s never sent. Therefore, they will monitor and enforce a spam threshold based on user complaints.

Yahoo said it has been measuring reported spam rates for a while and even sharing that data with trusted senders, but that starting in 2024 it would take action against anyone who exceeds a certain level of unwanted email.

Although they didn’t publish an exact number, it’s likely to be similar to Gmail’s or other providers’ (that is, a very small fraction of users marking your emails as spam).

In practice, what does Yahoo do if you send spam?

They can limit the number of emails they accept from your domain, send your messages directly to the spam folder, or even temporarily block your sends if the problem continues.

In fact, Yahoo announced that in February 2024 it would start enforcing certain standards for all senders, especially authentication and low complaint rates, and would gradually tighten enforcement during the first half of the year as senders adapted.

By mid-2024, they expect all bulk senders to support one-click unsubscribes and comply with the new rules.

· What should you do if you send many emails to Yahoo or AOL users?

Exactly the same as with Gmail: implement authentication protocols on your domains and follow good sending practices.

Yahoo published a Sender Best Practices guide on its Sender Hub and even offers a support contact to help senders adapt.

In summary:

• Set up SPF, DKIM, and DMARC. This is non-negotiable for Yahoo too. Check your domains with a tool (for example, there are free DMARC checkers) to make sure you have the right records and your emails are signed. Like the others, Yahoo will block emails from domains that aren’t properly identified.
• Send relevant content only to real subscribers: Yahoo stresses sending “only emails our users want”. That means not sending unsolicited emails. You need the recipients’ permission (for example, they subscribed on your website, or they’re customers who agreed to receive emails).
• Also, stick to the frequency you promised: if someone signed up for a monthly newsletter, don’t start sending them daily emails. And of course, don’t buy or sell email lists – that practice usually ends up giving your domain a bad reputation, because those people aren’t expecting your messages.
• Include a visible, working “unsubscribe” option: make sure any Yahoo user can easily unsubscribe. As we mentioned, Yahoo asks that they be off your list within two days, so your system must handle it quickly. After that, don’t send them any more emails (except perhaps a final confirmation that they’ve been unsubscribed, if appropriate). Ignoring unsubscribe requests doesn’t just annoy users; it also leads to formal complaints and blocks.

Ultimately, Yahoo has aligned its policy with Gmail’s: mandatory authentication, easy opt-out, and zero tolerance for spam.

Their stated goal is to improve the email experience for all users, and they trust that these measures (along with the cooperation of legitimate senders) will help create safer, more useful inboxes.

Conclusion: Similarities and differences between Outlook, Gmail, and Yahoo

The three major email providers – Outlook (Microsoft), Gmail (Google), and Yahoo (including AOL) – share a common vision: to make email a safer, more reliable, and spam-free channel.

To do this, they are raising the standard for what is expected from senders who send a large number of messages daily.

Generally speaking, there are more similarities than differences in their requirements:

· Sender authentication

This is the fundamental pillar in all cases.

Outlook, Gmail, and Yahoo now require you to prove the identity of your emails through protocols like SPF, DKIM, and DMARC.

What was once “optional” has now become a mandatory requirement when sending high volumes of email.

All three providers want to see authenticated emails with aligned domains; otherwise, those messages will likely end up in the spam folder or not be accepted at all.

The good news is that once they’re set up, these systems also benefit legitimate senders: for example, they help prevent anyone from sending emails pretending to be your company, which protects your brand and your users.

· Facilitating unsubscribe and user control

Another shared point is putting the user in control of what they receive.

Gmail and Yahoo were very explicit in requiring a one-click unsubscribe mechanism in bulk emails, with requests honored within 48 hours.

Outlook, although it framed it as a hygiene recommendation rather than a strict requirement, highlights exactly the same thing: a clear opt-out link in your emails.

In the end, they all point to the same thing: if the recipient no longer wants your emails, you must give them an easy way to stop receiving them.

This not only avoids frustration but also reduces the chances of your messages being marked as spam (which helps you maintain a good reputation).

In summary, “make it easy to say goodbye” is the shared motto.

· Only send wanted content (avoid spam)

The providers agree that the best email is one that was requested: the kind the user expects because they subscribed or find it relevant.

That’s why all three are monitoring spam rates and the quality of email lists.

Gmail set a specific percentage (a maximum of 0.3% complaints) as a benchmark, Yahoo talked about enforcing a similar spam threshold, and Outlook warns that it will take action against those who engage in bad sending practices.

In practice, they all want you not to send unsolicited emails: no buying databases, no continuing to bother people who no longer engage.

They also share the idea of proactively managing bounces and complaints (for example, by removing addresses that always bounce or inactive users).

Don’t worry about this, because Mailrelay does it automatically.

The common ground here is clear: if you abuse email and send spam, your messages will be filtered or blocked. If you’re responsible and only send to people who asked for it, your chances of reaching the inbox are much higher.

· Industry collaboration:

It’s worth mentioning that these companies are acting in coordination.

In its announcement, Yahoo included a quote from Google supporting these measures, and Microsoft joining in 2025 reaffirms that consensus.

A kind of unified standard is on the way: what Gmail and Yahoo started requiring in 2024, Outlook follows in 2025, and other providers will probably adopt it too.

For senders, this means that whatever you do to satisfy one will work for all of them.

If you configure SPF, DKIM, and DMARC on your domain and maintain clean sending practices, you’ll be complying simultaneously with Outlook, Gmail, Yahoo, and any other serious email service.

On the other hand, if you neglect any of these aspects, you’re likely to run into problems with several services at once.

Regarding differences

They essentially boil down to when and how the rules are enforced, rather than the content of the rules themselves:

· Implementation timeline:

Gmail and Yahoo rolled out their requirements starting in February 2024, with gradual enforcement over the following months (for example, Gmail began rejecting part of the email that didn’t meet these rules in April 2024, and Yahoo tightened its controls during the first half of 2024).

Outlook, on the other hand, joins a year later: it starts filtering to spam in May 2025 and plans to reject emails later on.

This means that in 2024 Outlook didn’t yet strictly require SPF/DKIM/DMARC for all large senders, but Gmail and Yahoo did; starting in 2025, all three will.

If you’re a sender, the best thing is not to wait: the sooner you adapt, the better, so you avoid problems now and in the future.

· Initial approach:

Gmail and Yahoo clearly set the threshold at 5,000 emails a day to their users for someone to count as a “bulk sender”.

Outlook also uses that figure (5,000 a day) to define the large senders covered by this policy.

The difference is that Gmail/Yahoo made it clear that only messages to their domains count (@gmail.com, @yahoo.com, etc.), while Outlook talks about domains that send 5,000 messages in general (although presumably its main concern is what reaches Outlook.com).

In any case, the number is similar.

Another small difference is that Gmail already required some authentication even at smaller scales (since 2022–2023 it started filtering messages with no SPF or DKIM), but the new requirement makes it mandatory for high volumes and includes DMARC.

Until now, Outlook allowed perhaps more flexibility for small senders, but is now aiming to raise the standard for large ones.

In essence, there isn’t much difference: all three agree that 5,000 a day is the point at which they get very strict, although even if you send less, following these practices is highly recommended for better deliverability.

· Additional technical requirements:

Gmail explicitly mentioned things like using TLS (encrypted email) and configuring PTR records (reverse DNS), while Outlook and Yahoo didn’t highlight this in their communications.

However, these technical details are common best practices across the industry.

It’s not that Outlook doesn’t want them; it likely assumes they’re part of proper server configuration.

Gmail just documented it more thoroughly.

But again, this doesn’t change the essence: a serious sender must use reliable servers with correct DNS and secure connections.

In conclusion, Outlook, Gmail, and Yahoo ask for practically the same things to avoid sending your emails to spam.

They want authenticated, responsible senders.

In summary, to avoid landing in the spam folder, you must:

• Configure authentication (SPF, DKIM, DMARC) on your sending domains – this is crucial for all these platforms.
• Follow best practices with your subscribers: only email those who opted in, make unsubscribing easy, manage complaints — in short, don’t be a spammer, even by accident.
• Give users control: a clear “unsubscribe” link in every bulk email, and respect the user’s decision promptly.

By adopting these measures, you won’t just comply with Outlook, Gmail, and Yahoo’s policies – you’ll also improve the deliverability and trustworthiness of your emails overall.

It’s about sending emails that people want to receive, securely and transparently.

If you succeed, your messages will have a much better chance of landing in the inbox and not the dreaded spam folder.

Monitoring your spam rate in email marketing and your inbox placement rate will help you check whether these measures are working.

Jose Argudo

CMO at Mailrelay. Writes about email marketing, copywriting and conversion for small businesses and entrepreneurs.

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