Difference between Indy 9 and Indy 10 in Authentication?

Hi @ all,
i have a program which sends protocol-files via eMail. It works since
nearlly two years with Indy 7 or Indy 9 (I don't know the version which
comes with Delphi 6 Pro). Now i switched  to Indy 10. The Problem
begans. While the program with Indy 9 can send the eMails without any
error, i now get the error message "Authentication unsuccesful". Same
User-Account and Password for the SMTP-Server. Only the difference
IdSMTP.UserID (Indy9) and IdSMTP.Username (Indy10). The rest of my code
is identical.
What's that? Why? How can i resolve it? Any ideas?

Thanks in advance
Klaus Dewald