Lync 2013 front end service not startting after migrating users.

We had an issue with a customer that was kind of a nut to solve.
We imported multiple AD users to Lync via a powershell script.
The script worked perfectly and the users seemed to have been imported correctly.
But some days later we restarted the Lync servers in the front end pool.
Then the lync front end service would not start and was stuck at starting.
Some errors in the eventviewer indicated trouble in reading some of the users SipURI.
It turned out that when importing the users some of them had special characters in the SipURI.
Characters like #/() and so on...
Powershell does not filter this and imports them anyway. (typical powershell feature)
So when Lync starts to read the user database it stops because the user SipURI is invalid.
You cannot have a special character in the SipURI.
Soulution is to manually edit each one of the users manually and then start the front end service.
And furthermore when importing from AD it's always useful to do some extra scripting to "wash" objects like SipURI.