It simply means the username it's trying to sync to mambo has the same email which is already existing in mambo.

If you are using 1.3.1.3, the username is displayed on the error message. You have to change the email for that username manually or from smf user administration.

Ok i now see who's email address caused this.
But now I get one after the other with messages like:
Syncing username Cobra-BOM- Failed! Please enter a valid Username:. No spaces, more than 2 characters and contain 0-9,a-z,A-Z

And it's not just one..... 

But the module option is set to use the Mambo module for regsitration?!
Registration module to use: >Mambo  CB (Mambo is selected)

How could they register with spaces, symbols or short names? 


So you mean I can't use the sync anymore?
Is there no need to use it then, because I though I needed to sync!? 

I started Mambo at the same time as SMF.
Up till yesterday everything worked OK with +/- 200 registered members.
But we recently had a lot of new members (+/-300) and that's when the error occured.

But the module option is set to use the Mambo module for regsitration?!
Registration module to use: >Mambo  CB (Mambo is selected)
How could they register with spaces, symbols or short names?

Thanks for the quick replies