The latest release of Office Outlook 365, Version 2001 (Build 12430.20184) broke the command line switch /m. This switch allows users to send mail using a command line:
outlook.exe /c ipm.note /m "firstname.lastname@example.org&Subject=Subject&body=nothing to see here"
After installing the update, the command line adds the subject and other fields to the To line of a new message.
This is not a bug, it will not be fixed. This permanent change is "by design" so that Outlook is compliant with RFC 6068. You will need to use a ? (question mark) after the email address, not a # (hash/pound sign).
Information passed using /m switch needs to be formatted using the mailto uri scheme in RFC 6068. Previous versions of Outlook incorrectly processed hfield values before the required “?” delimiter was specified. This has been corrected in the most recent version of Outlook. As outlined in the RFC only all data before the “?” delimiter is treated as part to portion of the mailto uri.
Use this as the command line:
Or use this with PowerShell:
Start-Process "mailto:email@example.com?Subject=testing This&Ccfirstname.lastname@example.org&Body=nothing to see here."
While this change will not be back ported to older versions of Outlook, the links that work in Outlook v2001 will work in older versions too.
Roll back to a previous build
You can temporarily rollback to the previous build while you update applications to use the new format. Don't forget to disable automatic updates.
Right click on the Start button and choose Command Prompt (Admin). If you don't see Command Prompt on the menu, you'll need to type cmd on the Start screen to find the Command Prompt then right click on it and choose Run as Administrator.
Paste the following line in the command prompt and press enter.
"C:\Program Files\Common Files\microsoft shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.12325.20344
For more information and screenshots, see Uninstall Updates in Office 'Click to Run'