GPG Key not available for Local Apt Repo

We have an Apt-mirror server.
We have also a custom repo named 'local' on this server.

If I add in sources.list the following line :

deb http://aptmirror.example.com/local trusty main

The following error is displayed :

W: Erreur de GPG : http://aptmirror.example.com trusty InRelease : The following signatures couldn't be verified because the public key is not available : NO_PUBKEY 2ED3267B70B1ADC4

Even with the following command :

gpg --keyserver aptmirror.example.com --recv-keys 2ED3267B70B1ADC4
gpgkeys: key 2ED3267B70B1ADC4 can't be retrieved
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

I tried also with apt-key adv but it's not working..

Do you know how to have this local GPG Public key available for all Linux clients ?

Attempts

gpg --send-keys --keyserver keyserver.ubuntu.com $GPGKEY

or

gpg --send-keys --keyserver keys.gnupg.net $GPGKEY

but I got :

gpgkeys: this keyserver type only supports key retrieval
gpg: keyserver internal error
gpg: keyserver send failed: keyserver error

And Copy-Paste with gpg --export --armor is not really a solution, with 200 computers

EDIT :
Thanks for your answers.

I tried this :

gpg --send-keys --keyserver keyserver.ubuntu.com $GPGKEY

OR

gpg --send-keys --keyserver keys.gnupg.net $GPGKEY

but I got :

gpgkeys: this keyserver type only supports key retrieval
gpg: keyserver internal error
gpg: keyserver send failed: keyserver error

And Copy-Paste with gpg --export --armor is not really a solution, with 200 computers …