mutt: "Couldn't lock /home/{{user}}/Mail/sent"

I'm trying to get mutt working on ubuntu, but I keep getting the error:

"Couldn't lock /home/{{user}}/Mail/sent"

when i try to send mail. My permissions for ~/Mail is drwxrwx---. I would really appreciate any advice on how to solve this.

I'm using bash for windows. Below you can see a excerpt of my .muttrc file.
I've left out stuff for security.

set folder = "imaps://exchange.ku.dk:993/"
set spoolfile = "+INBOX"
set postponed="+[ku]/Drafts"
set record="~/Mail/sent.lock"
set header_cache=~/.mutt/cache/headers
set message_cachedir=~/.mutt/cache/bodies
set certificate_file=~/.mutt/certificates
set move = no
set editor = 'vim'
set timeout = 10

Answer

My suspicion is that another service is blocking the file from being locked. Actually, you seem to be relaying your mails (as per your folder directive in your .muttrc file).

That will probably use Postfix underneath for the mail get relayed, and that's where I suppose the culprit is. Ubuntu systems come with a system to confine services to do only what they are allowed to do, and when you install Postfix it will automatically create a basic configuration for it (which doesn't include anything that you might do with mutt, of course).

To quickly test it, you might stop the apparmor tool by invoking:

• If you're using Ubuntu 14.04 or prior:

  
  

  /etc/init.d/apparmor teardown
  




• If you're using Ubuntu 16.04 or subsequent:

  
  

  systemctl stop apparmor
  

Then, try using mutt again. If it works, my assumption is right. In that case, you would need either to:

• Not define the Postfix configuration file in apparmor. For that, simply go to /etc/apparmor.d, find the postfix file under that tree and delete it, restart apparmor and you're done.


• Define Postfix configuration and extend it with your mutt additional configuration. For that, I recommend start learning here.