If it uses SMTP, and POP or IMAP then yes.

lf what uses smtp and pop or imap? outlook? icloud? and how do i tell?

The email server hosting your mac.com email account. I can't make any sense of how it relates to icloud.

According to this

https://support.apple.com/en-us/HT202304

it offers smtp and imap.

icloud is apple. any apple email address - mac.com, me.com, icloud.com, etc. -- is icloud. i downloaded thunderbird and it gets my mac.com emails, but i'm not sure it does anything more than outlook, which ties up my bandwidth for any other use by downloading my 12k emails every time i open it. does thunderbird do that too?

It will want to do it once, yes. That's how IMAP works; it wants to store messages on a server and show you what you have on the server inside the email client. If there is any way of throttling or limiting such a download to a date range then that would be a function of the server.

But in the account settings in Thunderbird, you can go to Synchronization & Storage, and set it NOT to store messages locally. I really don't know how that works because if it doesn't at least list the messages stored on the server then they may as well not exist. So I'd guess it downloads enough header info to identify each stored message. Over and above this there are settings to subscribe to specific folders, so if you have arranged for old messages to be in separate folders you could choose not to subscribe to those folders.

thanks.