Will a .si domain hurt my email deliverability? (2026)

Clerion Research Team27 October 202611 min read

No. As of October 2026, .si domain email deliverability is no worse than .com's: .si is not on public spam TLD lists, and inboxes judge history, SPF, DKIM, DMARC and complaints. The real risk is that most .si names are weeks old, so warm them up slowly.

Bright blue blurred gradient banner fading to off-white, reading .si domains and email

No. As of October 2026, a .si domain will not hurt your email deliverability just because it ends in .si. Gmail and other inbox providers judge .si domain email deliverability like any other: by sending history, authentication and complaint rate, not the extension. The real risk is that any .si domain bought this autumn is brand new, and new domains start with no reputation at all.

That last sentence is the part most founders skip. If you bought a .si name after the September 2026 "super intelligence" order and plan to send onboarding mail from it next week, you are not fighting the TLD. You are fighting the calendar.

This post is the follow-on to our guide on things to know before you buy a .si domain. That one covers the brand question. This one covers the inbox.

Does the TLD of my domain affect email deliverability?

Only a little. Spam filters treat the extension as a context clue, not a verdict. Deliverability firm Suped puts it plainly: a receiver "does not usually reject mail because a domain ends in a specific TLD." Domain age, sender reputation, SPF, DKIM, DMARC, the links in your mail and complaint history carry far more weight.

Where the TLD does matter is at the extremes. A handful of cheap extensions are so full of junk that some filters add points to anything sent from them. Suped's analysis of listed domains from October 2025 to March 2026 names .top, .cn, .cc, .cfd, .bond, .xyz and .sbs among the worst by raw count, with .cfd showing the highest listing rate at 17.54%. Suped also notes there is "no universal list of TLDs that always go to spam."

.si is not on any of those lists. That is the good news. The rest of this post is about why it is not the whole story.

Is .si on any spam or abuse blocklist?

Not on the public lists we checked, as of October 2026. Slovenia's .si does not appear in the top 20 spam TLD tables from the Cybercrime Information Center for March to May 2026, and Netcraft reported no rise in .si phishing after the September rush. Those tables lead with .com, .top, .cn, .info and .cc.

Here is what the Cybercrime Information Center report shows for March 1 to May 31, 2026, ranked by number of domains seen in spam reports:

Rank	TLD	Spam domains	Spam domain score
1	.com	829,715	50.9
2	.top	630,191	972.8
3	.cn	283,487	233.9
4	.info	204,909	386.8
5	.cc	135,041	538.9
Not in top 20	.si	n/a	n/a

Two things stand out. .com has the most spam domains by far, because it is the biggest zone. And the score column, which adjusts for size, is where the real outliers show up: .top scores almost 20 times higher than .com. A clean extension with a small zone, like .si was before September, simply never shows up.

Netcraft's October 1, 2026 report said it had "yet to see an increase in malicious content such as phishing" tied to the rename. OVHcloud's brand note from October 7 repeats that fraud on .si "remains low."

If the TLD is fine, what hurts .si domain email deliverability?

Newness, not the extension. Inbox providers have no history for a domain registered last month, so its first emails get extra scrutiny. Google's own guidelines tell senders to start at low volume with engaged users and warn that suddenly doubling volume "could result in rate limiting or reputation drops."

Most .si names that matter to founders were bought in the last five weeks. That puts them in the same spot as any fresh .com: no age, no sending record, and no Postmaster Tools data. A clean extension does not change that.

Say you run a small AI meeting-notes tool. You moved your site to notes.si on October 3 and want your welcome emails to come from hello@notes.si. On day one you sign up 300 people from an X thread, and your app fires 300 welcome emails, 300 "verify your email" links and a few dozen password resets in a single hour, all from a domain Gmail has never seen. That spike is what gets throttled. If the same mail came from your old .com, which has two years of quiet history, it would sail through.

How did the 2026 .si rush change the risk?

It added noise around the extension. Registrations jumped from about 100 a day to over 13,000, just over half the names tracked at one registrar were listed for resale, and phrases like "bank" and "pay" started showing up in new .si names. None of that is abuse yet, but filters watch fast-growing zones closely.

The numbers, all from reports published in the last month:

Volume. Register.si's 24-hour count went from 4,794 on September 23 to 13,603 on October 1, and the total zone grew 21.6% in eight days, per Netcraft. TechCrunch reported 11,000 new .si addresses on September 30 alone, the day after the order was signed.
Baseline. Domgate puts a typical September day at about 100 new .si names before the UN speech.
Speculation. Netcraft found just over half of the .si names it tracked at one large registrar listed on the aftermarket.
Risky words. Since September 19, ABT Domain counted 37 new .si names containing "bank", 119 containing "pay" and 16 containing "gov", according to Domgate.
Lookalikes. OVHcloud counted more than 44,000 names that exist in both .si and .ai, about 22% of all .si domains. On a QWERTY keyboard, "s" sits next to "a".

That last point cuts both ways. If you own acme.ai, someone else may own acme.si, and they can send mail that looks a lot like yours. Spoofing from a lookalike can hit your reputation, not theirs, if you have no DMARC policy telling inboxes what to reject. That has not become a .si problem yet. It is the thing to watch.

Should I send email from my .si domain or keep my old one?

Keep sending from the domain that already has history, and move mail to .si slowly. If your .com or .ai has sent clean email for months, use it for login, password reset and receipts while the .si domain warms up. Switch over only once the new domain has a few weeks of low-complaint mail behind it.

Our view, ranked by how much each factor will move your inbox placement on a new .si domain:

Factor	How much it matters	What to do
Domain age and sending history	High	Start small, ramp over weeks
SPF, DKIM and DMARC set up and aligned	High	Publish all three before the first send
Spam complaint rate	High	Stay under 0.1%, never reach 0.3%
Links and tracking domains in the email	Medium	Link only to your own domain
Lookalike or spoofed versions of your name	Medium	Set DMARC to quarantine once mail is stable
The .si extension itself	Low	Nothing, as of October 2026

Splitting by job also helps. Many teams send product mail from a subdomain such as mail.notes.si, so a bad newsletter week cannot drag down password resets.

How do I warm up a new .si domain for email?

Publish SPF, DKIM and DMARC before you send anything, then start with a small volume to people who expect your mail and grow it gradually. Watch spam rate in Google Postmaster Tools as you go. Gmail's limit is a spam rate under 0.3%, and Google advises staying under 0.1%.

The rules come straight from Gmail's sender guidelines, in force since February 1, 2024:

Every sender needs SPF or DKIM, valid forward and reverse DNS, and TLS. DKIM keys must be at least 1024 bits, and Google recommends 2048.
Bulk senders, meaning more than 5,000 messages a day to Gmail accounts, also need DMARC (a policy of p=none is accepted), alignment between the From domain and SPF or DKIM, and one-click unsubscribe on marketing mail.
Ramp gradually. Google says the more you send, the more slowly you should increase, and to send at a steady rate rather than in bursts.
Back off on errors. If Gmail returns SMTP error 4.7.28, Google says to stop for at least 10 minutes, then resume from one connection.

Back to notes.si. A sensible first week is your own team, then the people who signed up most recently, then everyone else. Send welcome mail as people arrive instead of in one batch. You are not trying to hit 5,000 a day. You are trying to give Gmail a quiet, boring history.

What can get a .si domain deleted or spoofed?

Fake owner details and lookalikes. The .si registry checks holder data and, under its terms, wrong details or fake privacy services can lead to a domain being deleted, which kills its email overnight. Lookalike .si names can be used to spoof you, so DMARC on your real domain matters.

The registry, Register.si, run by Arnes, began asking all holders to update their data in September 2018, according to registrar Openprovider. Holders using non-existent privacy services or dead email addresses were in breach of its terms. If you bought your .si through a cheap reseller with throwaway contact details, fix them now. A deleted domain is a deliverability problem no warm-up can solve.

For spoofing, DMARC is the tool. Start at p=none so you get reports, read them for a couple of weeks, then move to quarantine once you are sure only your own services send as you.

How do I tell if my .si email is landing in spam?

Check three places: Google Postmaster Tools for spam rate and domain reputation, your email provider's bounce and complaint logs, and a seed test where you send to your own Gmail, Outlook and Yahoo inboxes. If the welcome email lands in spam for you, it lands in spam for new users.

The fourth sign shows up on your site. A sudden drop in people finishing sign-up, while traffic stays flat, often means the verify email never arrived. That pattern is easy to miss if you only look at visitor counts.

Do this tonight

Run dig TXT yourname.si and dig TXT _dmarc.yourname.si. If you see no SPF record or no DMARC record, add them before you send another email.
Add the .si domain to Google Postmaster Tools so reputation data starts building now.
Keep login, reset and receipt mail on your older domain until the .si one has two to four weeks of clean sending.
Log in to your registrar and check that the holder name and email on your .si domain are real and current.
Search for your name on .si and .ai. If someone holds the lookalike, note it and set DMARC to quarantine once your own mail is stable.

If you have moved your site to .si as well, it is worth watching whether the new domain still gets found and cited. Clerion reports ChatGPT, Perplexity, Claude, Gemini and Copilot as their own channel and shows the step where sign-ups drop out, from one script tag and with no cookies.

Things to know before you buy a .si domain: the brand and registry basics.
How do I register a .si domain, and what does it cost?: registrars, prices and steps.
Who controls the .si domain, and is it safe to build a brand on?: who runs .si and what that means for you.

Frequently asked questions

Is .si a spammy TLD?

No. As of October 2026, .si does not appear in the top 20 spam TLD tables from the Cybercrime Information Center for March to May 2026, and Netcraft reported no rise in .si phishing after the September registration rush.

Can I use a .si domain with Google Workspace or other email providers?

Yes. A .si domain works like any other domain for email. You add MX records from your provider, then publish SPF, DKIM and DMARC records in DNS before you send. Nothing about the extension blocks it.

How long should I warm up a new .si domain before sending onboarding email?

Google gives no fixed period. Start with low volume to people who expect your mail, send at a steady rate, and grow gradually while your spam rate stays under 0.1% in Postmaster Tools. Two to four weeks of clean sending is a sensible floor for critical mail.

Do I need DMARC on a .si domain?

If you send more than 5,000 messages a day to Gmail accounts, Gmail requires DMARC. Below that it is still worth setting up, because lookalike .si and .ai names make spoofing easier. Start at p=none, read the reports, then move to quarantine.

Should I move all my email to .si after rebranding?

Not at once. Keep login, password reset and receipt emails on the domain that already has sending history, and move mail to .si gradually once the new domain has a few weeks of low-complaint sending behind it.

Can a .si domain be deleted for wrong owner details?

Yes. The .si registry asks holders to keep their data correct, and under its terms incorrect details or fake privacy services can lead to a domain being deleted. Check the holder name and email at your registrar.

Sources

.si domain email deliverability.si domainsuper intelligenceemail deliverabilitydmarcdomains