`mail_crypt` Doesn't Appear to be Working

[jordan.h at startmail.com]

Dovecot version: 2.2.22 (fe789d2)

I generated an EC key from the page https://wiki2.dovecot.org/Plugins/. For 
reference here's my /etc/dovecot/conf.d/10-mail-crypt.conf file:

----
mail_plugins = $mail_plugins mail_crypt

plugin {
    # mail_crypt_global_private_key = </etc/dovecot/ecprivkey.pem
    mail_crypt_global_public_key = </etc/dovecot/ecpubkey.pem
    mail_crypt_save_version = 2
}
----

I saw in a previous message on this mailing list that messages can be 
encrypted without the private key, so it's stored elsewhere. :-)

After restarting dovecot and sending myself a message I found that the message 
was still unencrypted. Nothing in /var/log/dovecot/*.log files or syslog 
indicated any problem loading the plugin (I even made some mistakes with the 
filename beforehand, and errors indicated it was trying to find the plugin).

In case in matters dovecot was installed as part of the automated iredmail  
install (https://iredmail.org). I didn't modify the dovecot.conf file after 
installation (except for thinking I needed to add `mail_crypt` to `plugins`, 
then figuring I didn't).

Any help is appreciated.

Thank you.
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