I cannot boot into my main hard drive and need to get saved mail from it to a new drive that I have set up. How do i copy all of my mail over from the old drive to the new. I can see all of the files on the old drive, just can't boot into it.
f you are talking about Apple's Mail app;
1. Look in the Users/"your UserName"/Library/ There is a Mail folder and
2. one Apple Preference file, "com.apple.mail-shared.plist" in the Users/"your UserName"/Library/Preferences folder.
3. You can probably setup the required network/mail items again, but it may save some time/ work to copy other related "com.apple.xxxx" files too, such as:
com.apple.AddressBook.plist, com.apple.internetaccounts.plist, etc. etc.
I am by no means an expert in "mail" so there may be other files required, sorry for the non-expertise!