mutt command line with gpg

[Meenal Pant <mpant@xxxxxxxxxxxxx>]

Hello,
I want to use mutt as a command inside a script and therefore I don't
want to  run mutt  interactively.
To achieve this, I use:
$> mutt -F ./.muttrc -s "Hello" -i ../text.txt   xxx@xxxxxxx </dev/null
and get the desired result.
My problem occurs when I use GnuPG and want to sign the message. I use 
set pgp_autosign=yes and define the signature key,  set
pgp_sign_as=0x127533B2 in .muttrc
The message does not appear signed to the recipient. However when I use
the same command without </dev/null and use mutt interactively then the
message appears signed.  Please help me fix this issue. Thanks

Also is their a way to encrypt and sign using GnuPG and Mutt via command
line ?

Thanks
Meenal