Keys
The global settings are fixed, the only things you'd wanna change are the paths to the .exe or mailbox files, and the DWORD for on/off. I've tried to do exclusion by adding a subkey "Exclude" and entering the strings & values for the .mbx'es but ies don't no gggvvvoorrk.
That's it.

Adding settings for Eudora: HKLM_SW_AD\Agents\MHEudora
The branch consists of global settings and location info in the only subkey ROOT\0.

"DLL"="pav_mheud.dll"
"Type"=dword:00000003
"Name"="Eudora Mail"
"Enable"=dword:00000001
"MailPath"="DRIVE:\\Program Files\\Qualcomm\\Eudora"
"ExePath"="DRIVE:\\Program Files\\Qualcomm\\Eudora"
"CtrlFileExt"=".TOC"
"MailFileExt"=".MBX"


AgentsMHEudoraRoots0
"Partial"=dword:00000001
"Name"="Eudora Mail"
"Path"="LFN PATH"

Adding settings for Exchange Mail: HKLM_SW_AD\Agents\MAPI
The branch consists of global settings and if you use it location info in the only subkey ROOT\0.

"DLL"="pav_mapi.dll"
"Type"=dword:00000001
"Name"="Exchange Mail"
"Enable"=dword:00000000

Adding settings for Outlook Express/Internet Mail: HKLM_SW_AD\Agents\MHInternet
The branch consists of global settings and if you use it location info in the only subkey ROOT\0.

"DLL"="pav_mhint.dll"
"Type"=dword:00000005
"Name"="Internet Mail"
"Enable"=dword:00000000
"MailPath"=""
"ExePath"="%WINNTDIR%"
"CtrlFileExt"=".IDX"
"MailFileExt"=".MBX"

The branch consists of global settings and if you use it location info in the only subkey ROOT\0. Adding settings for Netscape Mail: HKLM_SW_AD\Agents\MAPI

"DLL"="pav_mhns.dll"
"Type"=dword:00000004
"Name"="Netscape Mail"
"Enable"=dword:00000000
"MailPath"="DRIVE:\\Program Files\\Nutscrape\\mail"
"ExePath"="DRIVE:\\program files\\Nutscrape\\program"
"CtrlFileExt"=".SNM"
"MailFileExt"=""