You can share a conversation with a colleague so they can read it in Newton and discuss it with you in comments. Comments stay inside Newton: the people on the email never see them.
Steps
Desktop
Open the conversation.
Click the share button at the top of the conversation (Share this thread).
Type an email address in Add person by email… and click Add. The conversation is shared as soon as you add the first person.
To comment, click Comment at the bottom of the conversation, write your comment and click Post comment. Type @ to mention someone.
To stop sharing with someone, click the share button again and click the remove button next to their name.
iPhone, iPad & Android
Open the conversation.
Tap the share button at the top.
Type an email address in Add person by email… and tap Share.
To comment, tap the comment button at the top, write your comment and tap Post. Type @ to mention someone.
To remove someone, open the share button again, tap ⋮ next to their name and tap Remove access. To stop sharing with everyone, go to Shared by me, tap the conversation and tap Revoke share.
Conversations you share are in Shared by me, and conversations shared with you are in Shared with me, in the sidebar on desktop and the menu on your phone. Conversations shared with you also appear in your unified Inbox.
Good to know
People you share with can also reply to the conversation, and their reply is sent from your email address.
You can share a conversation with up to 10 people. Anyone who doesn't use Newton gets an email inviting them to create an account with that address.
Sharing works with Gmail and Outlook accounts. People can't open a conversation shared from an IMAP account, such as iCloud or Yahoo.