Short version: a SURBL listing has no practical impact on deliverability in 2026. If your domains show up on SURBL, there is no need to panic, pause campaigns, or make major changes — keep warming up and keep sending.
Why a SURBL listing is not a problem
Google has effectively stopped paying attention to SURBL, largely because it began flagging far too aggressively over the past year — to the point of affecting paid Google/Microsoft enterprise infrastructure and legitimate businesses. Google was the last of the major ESPs still consuming SURBL, and it stopped doing so within the last year. A couple of small providers may still consume SURBL-family lists, but their combined market share is small enough that it isn't worth planning around.
A real example from our own accounts: one client had 188 domains listed on SURBL and kept sending cold email throughout. Their reply rate did not change at all, and we continued to see solid spam-test results from those same listed domains.
A few important technical points:
SURBL lists the domain (URL reputation), not your sending IP.
Our sending IPs are not blacklisted — they stay green, and we rotate IPs automatically.
A SURBL "multi" listing in tools like MXToolbox or an Instantly warning ("contains a URL listed in the ABUSE SURBL blocklist") can be safely ignored; it does not reflect inbox placement. The same applies to similar link/URL-reputation lists such as SpamRATS.
Our own infrastructure domains show up on SURBL too — that's expected
If you run a full DNS/SPF audit, you may notice that the relay domains we include in your SPF record (the ones behind our sending infrastructure) are themselves SURBL-listed, not just your own domains. This is expected and not a sign of a platform-wide outage or a defect in your specific account.
Here's why it doesn't translate into a deliverability problem for you:
SURBL scores the domain shown in a URL inside a message body, not the server or IP that relayed the message. Our infrastructure domains being listed doesn't change how Google or Microsoft treat the IP your mail actually sends from.
We operate sending infrastructure at very high volume (80M+ emails/day), which is exactly the kind of footprint that tends to accumulate SURBL "abuse" listings over time even when actual inbox placement is healthy — the two are measuring different things.
Mailbox providers made the shift away from weighting SURBL industry-wide starting in late 2025 (see the SURBL blacklist explainer for more detail). AI-based audit tools trained on older data still flag SURBL as high severity, so you'll keep seeing it surfaced as "critical" in automated reports regardless of real-world impact.
If you're seeing this in a third-party or AI-generated audit alongside other findings (DKIM, DMARC, redirect checks), it's worth having us review the specific finding rather than treating the whole report as evidence of an infrastructure problem — some of those checks don't apply cleanly to how our managed DNS and custom-signed DKIM are set up.
"But my audience sits behind security gateways, or uses SpamAssassin"
This comes up most often from senders whose recipients are technical buyers — MSPs, IT and security teams — who run email security stacks in front of their mailboxes. The concern is reasonable, but it doesn't change the conclusion above.
A SURBL flag doesn't automatically mean SURBL is what filtered you. Every major provider inspects the links and content of a message anyway — a plain Google Workspace inbox runs its own link and content checks with no SURBL involved. So seeing a URL-reputation listing does not by itself identify the cause of a placement problem.
SpamAssassin is not a meaningful factor for B2B lists. We don't see SpamAssassin actively used on corporate mailboxes — it shows up mostly on self-hosted and open-source mail stacks. For a typical B2B recipient list, it's likely that effectively none of your leads are scored by it, which also means a SpamAssassin seed result is not representative of where your mail actually lands.
You can size your own exposure directly. Check the MX records of your lead list to see what share of your recipients resolve to Google or Microsoft versus a security gateway (Barracuda, Proofpoint, Mimecast, and similar). That MX breakdown is the honest measure of how much filtering-gateway exposure your audience really has — far more useful than reasoning from a blocklist flag.
What you should do
Keep warming up your mailboxes.
Keep your campaigns running — there's no need to pause, reduce sending volume, or otherwise change your strategy because of a SURBL listing. Just keep warming up and sending as usual.
Do not delete mailboxes or domains in reaction to a SURBL listing.
Spam-test results can still be positive even if your domain appears on SURBL, and there's no need to purchase new domains — SURBL-listed domains are still fully usable with Maildoso mailboxes.
Reference image: https://ibb.co/gLZjKKxt
Not the same as a registrar suspension
A SURBL listing is very different from a registrar/registry suspension, which is a hard block that stops a domain from resolving or sending until it is reinstated. If a domain is actually suspended (rather than just SURBL-listed), contact support to confirm the status and discuss options such as a replacement domain.
My domain is listed before I've even sent an email yet
It's normal to see a brand-new domain flagged on SURBL or a similar list like SpamRATS before you've sent a single campaign email — these lists often pick up domains from bulk registration/DNS patterns, not from anything you've sent. The guidance above applies the same way: this isn't a signal your domain is untrustworthy, and there's nothing to fix before you start warming up.
Seeing an IP flagged instead of a domain?
Everything above is about SURBL/URL-reputation lists, which flag domains, not IPs. If what you're actually looking at is a sending IP address showing as blacklisted, or a mailbox labeled "burned" or low-reputation, that's a different situation with its own guidance — see One of my sending IPs shows as blacklisted and My mailboxes show as "burned", "blacklisted", or low reputation — what it means.
Other deliverability questions
For deliverability topics beyond SURBL — inbox placement or spam diagnosis, warmup-flag issues, blacklist delisting requests, or "why are my results low" — please contact support so our deliverability specialist can review your specific account. You can also book a deliverability audit from the top-right option after logging in. If a blacklist flag is the reason you're considering a refund, see Domains flagged as blacklisted: how we help, and where refunds fit in.