How do you correct the apple mail "offline" problem

Question

Do a "P" "R" (Ram) Reset. Turn your computer off. Then as you turn it on immediately hold the P , R , Option, Command keys down all at the same time  ( all four) and keep holding until you hear two dong sounds and the screen go black for second and the Apple reappears. Then let off the keys.
OS X Yosemite: Reset your computer’s PRAM
If your Mac doesn’t seem to be remembering your speaker volume, display resolution, or the disk it should be using during startup, you may need to reset your computer’s PRAM.
Resetting PRAM may change some system settings and preferences. Use System Preferences to restore your settings.
Important:   To print these instructions, click the Share button in the Help window, then choose Print. 
Choose Apple menu > Shut Down.
Locate the following keys on the keyboard: Option, Command (⌘), P, and R. You will need to hold these keys down simultaneously in step 4.
Turn on your Mac.
Immediately press and hold the Option-Command-P-R keys. You must press this key combination before the gray screen appears.Continue holding the keys down until your Mac restarts, and you hear the startup sound for the second time.
Release the keys.
After resetting your computer’s PRAM, you may need to update your speaker volume, display resolution, and startup disk preferences. For more information about PRAM, see the Apple Support article About NVRAM and PRAM.

Answer 1

Hi, Jordan -
Welcome to Apple's Discussions.
If the original drive in the newer Mac is a Western Digital, its jumpers may be set to Single, which WD drives often use when there is only one device on the bus. When a second drive is added, the jumpers on the original must be reset to Master.
OS 9's utility is named Drive Setup - you should find it in the Utilities folder on the hard drive. Run that. Select the added hard drive in the list, then select Mount Volume from the Functions menu.
You can also check with that utility to see if the OS believes the drive has been set to automount at boot. Again, select the drive in the list. Then select Volume Settings from the Functions menu - there's a checkbox in that screen to set automount (for freshly initialized drives, that's turned on by default).
Also, try running Disk First Aid (should also be in the Utilities folder). Let it have a look at the second drive, and repair anything it can.
Apple System Profiler should report the format of all drives it sees. Is the format of the drive from the old Mac stated as Mac OS Standard, or as Mac OS Extended?