Hi @bartos123,
Firstly, you could initialize an array variable named EmailDomain to hold these Email domain store in the Excel file:

Secondly, use split() function extract domain form the Email address submit in MS form, I use "Test@gmail.com" to test, we should use split() function two times, first time could move "Test", second time could move ".com", finally it will remain "gmail":

In the end, use the Condition action with contains, to determine the EmailDomain whether it contains "gmail".
Best Regards,
Community Support Team _ Lin Tu
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