If your emails are bouncing or landing in spam for everyone, not just one recipient, check whether your sending domain or server IP is on a blacklist. Go to mxtoolbox.com/blacklists, enter your domain or IP, and run the check. It queries dozens of major blacklists (Spamhaus, Barracuda, SORBS, and others) at once and tells you exactly which ones flagged you.
Most blacklist entries clear on their own within a few days to a couple weeks once the underlying cause is fixed. Some require you to manually request removal. The fix depends entirely on why you got listed, so start there before you request delisting.
Domain blacklist vs. server IP blacklist
MXToolbox checks two different things, and it matters which one is flagged:
- Domain blacklist: your domain name itself is flagged, usually because of spam complaints tied to your content or sending patterns, or because your authentication records are missing or broken. See why are my emails going to spam for the authentication side of this.
- Server IP blacklist: the mail server's IP address is flagged. On shared hosting, this matters because you share an IP with other accounts on the same server. If another account on that server got compromised and started sending spam, the shared IP can end up blacklisted through no fault of your own.
Run both checks. A domain-only listing means the problem is your own sending behavior or your DNS records. An IP listing on shared infrastructure means the problem could be someone else entirely, which is a different fix and usually not something you can resolve yourself.
Why servers and domains get blacklisted
Blacklist providers flag based on sending behavior their spam traps and recipient reports pick up. Common triggers:
- Missing or broken SPF, DKIM, or DMARC records. Without these, receiving servers can't verify the mail actually came from your domain, which reads as suspicious.
- A sudden spike in outbound volume, often from a compromised account or a script that got out of hand.
- Sending to stale or purchased lists with a lot of dead addresses. Hitting spam traps (dead addresses blacklist providers seed specifically to catch this) is one of the fastest ways to get listed.
- High spam-complaint rates. Recipients marking your mail as spam repeatedly signals the same thing to filters as it does to humans.
- Open relays or weak authentication that let someone else send spam through your server.
Fix the underlying cause before requesting delisting. Blacklists that see repeated listings from the same source get slower to clear, and some track history.
How to request delisting
Once you've confirmed the root cause is fixed:
- Go back to mxtoolbox.com/blacklists and click through to each blacklist that flagged you. Each one shows a link or process for removal requests.
- Follow that blacklist's own delisting form. Some (like Spamhaus) require you to describe what caused the listing and what you changed. Others clear automatically after a set period with no new spam reports.
- Don't submit removal requests to every list from a bulk tool or third-party "auto-delist" service. Some blacklists penalize automated or repeated requests.
- Recheck a day or two later. Most delistings process within 24-48 hours; a few take longer.
While you're auditing authentication records to prevent a repeat, confirm SPF and DKIM are both present and correct. Both are auto-configured for Flashcloud-hosted email, and adding a DMARC record (not automatic, but recommended) gives receiving servers clear instructions on what to do with mail that fails those checks, which reduces the odds of a future listing.
When to contact support
Open a ticket from Support → New ticket in the portal if:
- You find your server IP (not just your domain) on a blacklist. This usually points to another account on shared infrastructure, and it's not something you can fix from your own DNS settings.
- Your SPF or DKIM records look missing or broken when you check Domains → click your domain → DNS, and you're not sure how to correct them.
- You've fixed the cause and requested delisting, but a listing hasn't cleared after several days.
Support is real humans via ticket or live chat, no phone line. If it's a server-level IP listing, we can see the full picture on our end and escalate to the blacklist provider directly, which is usually faster than an individual delisting request.