saved email files

I went looking for some information on my mac and found it, but I also found a lot of other information and was intrigued as to what it all was and where so I followed the files I was shown at the bottom of finder. most of it was from my emails I have saved on gmail. That means that when I was trying to set up my imap account for it I made a mistake and did a pop account. I believe this is right.
Is it safe to trash the folders so I don't have all that info and photos etc on this computer or will it download it again and again? If it is OK I understand that all I have to do is drag and drop to the trash, is that correct?