I think Its Bad Idea, Why not you show your Test case to vendor ,
You can also refer the Doc.Getting Started with Oracle Database
6.7.2 Minimum Requirements for Passwords
6.7.3 Recommendations for Passwords
Yes, use of @ character is also part of password protection.
Passwords containing any character other than alphabetical characters, numbers, and special characters. For example:
Check Keeping Your Oracle Database Secure link.
What happens when you says :