only load zlib when compression is used

core/dovecot/conf/dovecot.conf

@@ -21,7 +21,10 @@ mail_access_groups = mail
 maildir_stat_dirs = yes
 mailbox_list_index = yes
 mail_vsize_bg_after_count = 100
-mail_plugins = $mail_plugins quota quota_clone zlib{{ ' ' }}
+mail_plugins = $mail_plugins quota quota_clone{{ ' ' }}
+  {%- if COMPRESSION -%}
+  zlib{{ ' ' }}
+  {%- endif %}
   {%- if (FULL_TEXT_SEARCH or '').lower() not in ['off', 'false', '0'] -%}
   fts fts_xapian
   {%- endif %}