The Twitter Support sent me to the Customer Support and they sent me here.

I host my own VPN Server for my own personal use at OVH.
But when connected to it i am unable to login with the Minecraft Launcher, account.mojang.com and minecraft.net.
"Error! Unknown e-mail address or password."

When I use my home internet (without VPN) it works.

I have 3 IPs from OVH (in different subnets), i tried every one as VPN-exit. The IPs belongs to me since a long time (except the third) and are not blacklisted.
The problem is persistent i tried it several times over the last months - with the old and the new launcher.

On the same server runs a Minecraft server - he can verify the user logins without problem. Only client login is affected.

This are my IPs:
51.254.103.30
149.202.2.211
5.196.171.30 (i want to use this IP permanent as VPN exit)

I don't know what my neighbours in the subnets are doing.
Mojang either is blocking the whole subnets permanent or my neighbours are causing this "security bans" regularly.

https://help.mojang.com/customer/en/portal/articles/781529
"If your problem is not resolved after 24 hours, please contact customer support."
Now i'm here