A server can ban you up to 999 days.
You get a global ban if you are banned in several servers in a period of 30 days. I don't remember the exact number, it was something around 10~15 servers. You get a warning in the game and an email when you are getting close to that limit.
I guess you don't have to prove it, but play in servers that don't do stupid things like banning players without enough proof.

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Quote from cargame.nl :

Sounds like the ban system can be abused and/or is abused. Create some servers ban a name offline on these various servers and it gets a global ban.

I've always thought that the player needed to be online to get counted as banned, but now that I think about it I have never seen info on this regard.

Not gonna test it by myself

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In case you really did not know: It seems your cruise server is not always as legal as you think. I googled, they share hackcrack on facebook. They use nicer words but it is hackcrack.
From that email I would guess to make new install and wait 30 days.