[openpgp] Combining signature with signer's public key

[Kai Engert <[e-mail]>]

Is it possible to include the sender's own public key as part of a 
detached OpenPGP signature?

When Thunderbird sends a signed email, it wants to include the sender's 
public key by default, to ensure that the recipient has it available.

Thunderbird sends the key as an attachment.

We received a surprisingly high number of complaints from users. who are 
unhappy about having attached the key by default. Apparently having the 
extra public key attachment causes confusion on the recipient side, with 
users not understanding what the attachment is about.

However, I haven't heard complaints about the signature attachment - 
which is shown by MUA that don't support OpenPGP. The signature 
attachment appears to be less of a problem or confusion.

If it were possible to include the sender's public key inside the 
signature, Thunderbird could use a single attachment for both.

Thanks,
Kai