Gmail – How to insert a reply inline in Gmail

Sure, and it's pretty easy too:

1. Go to Gmail settings
2. Go to Accounts and Import Tab
3. Click on Send Mail from another address
4. Enter the Forward account address.
5. The email should send to that address which should forward back to your Gmail.
6. Complete the steps in the email.

When you send a new email you can now change the from address to your forward account.

Answering my own question, it turned out the problem was during switching from rich formatting to plain text:

• if previously I used plain text, Gmail will break long lines properly
• if previously I used rich formatting, Gmail will quote Outlook style, and when I press 'plain text', Gmail will reformat the reply to plain text, but long lines are not broken

So the solution if previously I chose rich formatting is:

• reply
• click 'plain text'
• discard
• reply again