How many domains will 1and1 host per account?

They offer 3 registrations but do they host more than that?

Ask them, not us - they have support team ... see their support page !

I am not the manager of this company, the other webmasters too

20 on their Beginner package, up to 200 on the Developer package. But that's on their web site. Look it up for more details.

My experiences with 1and1 we definately NOT 99.9% uptime.

If you need it, dont use them.