How can I make vim's flowing aware of email replies?

Question

Problem summary

I use vim to edit emails that I send with mutt. I also use format=flowed, which "reflows" text. That is, lines are limited to a fixed number of characters, and a "soft wrap" is applied, as indicated by the presence of a trailing space.

In vim, I have the following set:

setl tw=72
setl fo=aw

This sets the line length to 72 charaters, and sets up autoformatting with the trailing space. This works well in general. However, if I attempt to quote something with >, this character is not treated as a special character, and will be considered "inline" to the text.

Example

Copy the following text and paste it into vim.

Tempus. Vivamus. Dis natoque vitae erat. Consectetuer adipiscing nullam nec gravida non, at posuere enim, consectetuer ve. [1]

vim correctly breaks it into two lines, the first with a trailing space.

Tempus. Vivamus. Dis natoque vitae erat. Consectetuer adipiscing nullam 
nec gravida non, at posuere enim, consectetuer ve. [1]

I add > by selecting the lines and using :'<,'>s/^/> /, which results in the following.

> Tempus. Vivamus. Dis natoque vitae erat. Consectetuer adipiscing nullam 
> nec gravida non, at posuere enim, consectetuer ve. [1]

However, I now want to remove the [1] from the end, so I navigate to the end and delete. vim now reflows to the following, with the > "inline".

> Tempus. Vivamus. Dis natoque vitae erat. Consectetuer adipiscing 
nullam > nec gravida non, at posuere enim, consectetuer ve.

What's even worse is that I can delete the > manually and insert a new > before nullam, but this will immediately be reflowed to the previous line as follows.

> Tempus. Vivamus. Dis natoque vitae erat. Consectetuer adipiscing > 
nullam nec gravida non, at posuere enim, consectetuer ve.

Question

Is there a way to make vim's flowing aware of >? FWIW I've also tried this mail.vim customised for format=flowed, but it suffers from the same problems.

Answer 1

From one of my previous answers, you can get this to work if:

1. You have nb:> in your comments setting.
2. And you have q in your formatoptions setting.

So:

setlocal comments+=nb:>
setlocal fo+=q

After doing these, I get the expected wrapping:

> Tempus. Vivamus. Dis natoque vitae erat. Consectetuer adipiscing 
> nullam nec gravida non, at posuere enim, consectetuer ve.

Answer 2

setlocal formatoptions=jawtcqln worked for me. I'd put it in ~/.vim/ftplugin/mail.vim.