i.e. there appears to be no way to stop the entire mailbox from the server being downloaded.

I have installed TB on a new device and want to set up my mail accounts with only the last 3 months mail for each one. I understand the IMAP account settings for "Synchronization & Storage" & "Disk Space" where indeed you can set the download by size or time. The problem is that those settings are only accessible once the mail account is set up. The mail account set up itself initiates the download of all mail from the server the instant the account is set up which is then not adjustable until after that initial download is complete. i.e. there appears to be no way to stop the entire mailbox from the server being downloaded. Does anyone know a way to time limit that initial download or indeed prevent any initial download until the account settings can be used to do so?