Quick answer: Mojang's enforcement team is sending takedown emails to ISPs and hosting providers over swear words in server MOTDs, and the reports include private, whitelisted servers with three players that were never advertised anywhere. The emails give a 5 day deadline before the entire IP lands on Mojang's client-side blocklist. If it happens to you: change the MOTD, submit an appeal through Mojang's form, and based on current reports you are unblocked in about a day.
This week a thread on r/MinecraftServer blew up after someone shared the enforcement email their ISP forwarded to them. Their server is a whitelisted Folia server for a handful of adult friends. The MOTD contained one swear word that was an inside joke. The email listed the IP, the port, the offending word, a link to a public status checker as evidence, and a countdown.
Two details in that email are worth reading twice. First, Mojang states they cannot block a specific port, only the full IP. On shared hosting infrastructure that means one customer's MOTD can get an IP blocked that other customers are also using. Second, the email openly asks hosting providers to build MOTD scanning into their panels so violations "can be caught early". Mojang is asking hosts to pre-moderate their customers.
How the blocking actually works
This part is old, documented technology. The Minecraft client downloads a blocklist from sessionserver.mojang.com/blockedservers, a plain list of SHA1 hashes. When you click join, the client hashes the server address and IP you are connecting to and refuses the connection on a match. The system has existed since the EULA enforcement wave of 2016, it just used to be aimed at big commercial servers.
Two things follow from that design:
- The block lives in the client, not on your server. Your server keeps running fine, players just get a generic connection error with no explanation. One affected owner spent four hours debugging before figuring out the server had been blocked.
- It only stops unmodified official clients. Which tells you how much actual protection this adds, and how much collateral annoyance.
How does Mojang find a private whitelisted server?
Here is the uncomfortable part: your MOTD was never private. Any Minecraft server reachable from the internet answers a Server List Ping, and sites like mcsrvstat.us will show anyone your MOTD, version, and player count if they know the address. A whitelist controls who can play, not who can look.
How Mojang gets the candidate addresses in the first place is not confirmed, and the thread is careful to call it speculation. The two leading theories are that they collect source IPs from normal online-mode=true authentication traffic and then probe those IPs for a Minecraft service, or that they simply mass scan IPv4 space the way Shodan does. One data point makes the lazy version of theory one insufficient: a private server on port 25566 got blocked too, so if probing happens, it is not limited to the default port. Someone in the thread also reported a notice for a server running online-mode=false, which fits the scanning theory better than the auth traffic theory.
Practical conclusion either way: a non default port does not hide you, a whitelist does not hide you, and not advertising the server does not hide you.
What to do right now
Check your own MOTD today. Put your server address into a status checker and look at it the way an automated filter would. An inside joke between adults reads very differently to a keyword scanner, and the scanner is the one writing emails to your ISP.
If you want the MOTD out of public view entirely, set enable-status=false in server.properties. The tradeoff: your server shows as offline in everyone's server list, including your friends'. For a small private server that is often acceptable.
If you are already blocked: change the MOTD first, then submit the appeal form on Mojang's help site. Current reports put the unblock at roughly a day, with the email reply trailing a few days behind. Do not wait it out, the block does not expire on its own.
If you rent from a host, keep the MOTD clean even if you find the policy absurd. An IP block hits the address, not the server, and on shared infrastructure that address may not be yours alone.
Where we stand as a host
We think blocking a three player friend server over one word is using a sledgehammer on a walnut, and the request that hosts build MOTD scanners into their panels sits badly with us. We host your server, we are not your chat moderator. At the same time we cannot ignore IP-level blocks that would hit innocent neighbors on shared infrastructure, which is exactly the pressure Mojang is applying by refusing to block per port. So our honest advice is boring: keep the public facing text clean, put the inside jokes inside the server, and if you get one of these emails while hosting with us, open a ticket and we will sort it out with you.
FAQ
My server is whitelisted. Is my MOTD still public? Yes. The status ping that returns your MOTD answers before the whitelist is ever consulted. If the port is reachable, the MOTD is readable.
Does running a non default port protect me? Reports say no. At least one blocked server ran on 25566.
How do I know if my server has been blocked? Vanilla clients refuse the connection with an unhelpful generic error while the server itself runs normally. If friends suddenly cannot connect and nothing changed server side, check the blocklist before you start debugging plugins.
How long does an appeal take? Based on current reports, about one day for the unblock after you change the MOTD, longer for the actual email response.
Does this affect cracked or modified clients? The blocklist check happens in the official client. Modified clients generally do not enforce it, which says a lot about who this system actually inconveniences.