Using classic Outlook for Windows in business environments
Just FWIW only!
I used a 3rd party tool to 'extract' all sender-email addresses to a list.
Then removed all text before the '@' (so only @domain.com is left)
Then copied the list into Excel.
Removed duplicates and imported the list into safe senders list.
Suggest to check/tag the option "Automatically add people I email to ...."