In Mail how to search a particular mail box

Thank you for your helpful reply. But when i do that, it still searches ALL mailboxes instead of the ONE mailbox i want to ONLY search. I have ONE email in a particular mailbox with this special key word [which i am doing as an example/test] but when i select that mailbox, and type the key word in the search field, and select entire message [instead of name, subject], it gives me 118 emails with that key word from ALL mailboxes and including from Trash. My ONE email is amongst the 118 shown to me, but it is cumbersome to search through all 118. In the past, i could select a PARTICULAR mailbox and only search that limited mailbox, but now it searches ALL mailboxes PLUS trash. Any idea what i should try. Thanks so much. I really rely on how i used to be able to search in Apple Mail [and dont like resorting to Gmail where it does work as it should, mailbox by mailbox].

i tried to follow your directions more carefully and it worked this time! I typed the NAME of the mailbox in the search field, then clicked that was the mailbox i wanted, and THEN typed in the key word, and UP POPPED the correct ONE email. THANK YOU so much. This is a change tho. I used to just select or highlight the mailbox name on the left side of the screen in Apple Mail, and then merely type in the key word in the search field. So this is an added step to type the mailbox name in the search field, but hooray! It works. I really appreciate your help and pls correct me if anything further i should know about this.

hmmm, i maybe need to enlist my husband to look at your reply and plead with him to guide me. When i click on the left for the specific mailbox, and then only put the key word in the search field, once again the 118 emails come up [immediately after doing a search of that mailbox minutes earlier the way you told me to.....it did not stick with that mailbox in the next search]. The only way i could find that ONE email in the specific mailbox was to FIRST type the mailbox name in the search field, and click on the drop down confirming it was THAT mailbox, and then type the key word in the search field, and Voila, up came just one [the correct] email instead of 118 others from Trash etc. So i might be not understanding something and will have my husband read through your thoughtful replies to see if he can figure out why i am having to do this extra step that you don't necessarily always have to take in your experience unless you switch mailbox searches. Thanks and i will let you know if we work this out. Feel free to elaborate if you have any other observations on what i might be doing wrong! Thanks.

thank you so much! it worked! this helps me so much. my husband thanks you too since i stopped pestering him about how i could no longer search. I can now! Many thanks for your patience and help.