How to test external email notifications in a test instance

Summary:

Hello Team, I need to test some email notifications which are sent to suppliers / supplier users for POs, BPA etc. but I am not sure how can we create some test transactions and check it in a lower instance.

Content (please ensure you mask any confidential information):

Hello Team, I need to test some email notifications which are sent to suppliers / supplier users for POs, BPA etc. but I am not sure how can we create some test transactions and check it in a lower instance. Outbound email notifications are turned off in lower instance? Can anyone please let know how have you tested these notifications?