Sign outgoing mail as default

Hello

i like to setup a policy of sign all outgoing mail per default but do
not encrypt. Unfortunately the signing seams only to work if the
target domain (recipient) exists as remote domain.

Settings used:

- User with private key/cert and internal domain membership
- Settings are Encrypt mode "No Encryption" and "Only sign when
encrypt" is unchecked for this user and his domain.

If i create the remote domain the signing works if i delete it the
message does not get signed.

Is this intended behaviour or have i got something wrong?

Many Thanks

Andreas