To distribute a PGP public key, please use `p' on attachments in Draft mode. It asks whose public key you want to distribute. Just type `RET' if it is yours. If you want to distribute another person's, input his Email address with completion. The PGP public key will distributed as Content-Type: Application/Pgp-keys.
If Mew finds that the part is Application/Pgp-keys, it tries to add the PGP public key onto your PGP public keyring. Remember that Mew is careless about both TRUST and VALIDITY. It is YOU who set these values. Please use "pgp -ke" and "pgp -ks" to change them. If you don't know what TRUST and VALIDITY is, you should learn the web of trust system provided by PGP BEFORE using PGP to protect your privacy.