Hi!
I installed today eM client and my problem is, if i got 1 mail and i send answer, eM put answer into sent folder, it’s ok. But if after this i delete the original mail from the inbox, eM delete from sent folder too, but it’s not ok 
That is because you are deleting the conversation, which includes the sent message,.
Turn off conversations using Menu > View > Conversations > Disable Conversations, and see if that works better for you.