my hotmail is set up with Mail on my imac,I can receive the emails but can't send them from hotmail address what settings do I check?

Mac i5 , 27" mid 2011, , Processor : 3.1GHz, Intel Core i5, Memory 4GB 1333 MHz DDR3. running High Sierra v 10.13.3.

Have been able to send & receive email thru Mail for my hotmail address for years, suddenly (abt 12 months ago)

I can only receive emails but not send from the hotmail address I need to select my gmail and it goes fine, not how I want it, is there a solution,? I was going to delete the hotmail account then re enter it ( I don't have all the correct setting as I can't see then when I go into see the details of email accounts). would this work?

Barb😕