imap: doc and default config

DOCUMENTATION.md

@@ -812,6 +812,9 @@ Available backends:
 `dovecot`
 : Use a local Dovecot server to authenticate users.
 
+`imap`
+: Use a IMAP server to authenticate users.
+
 Default: `none`
 
 ##### cache_logins
@@ -993,6 +996,18 @@ Port of via network exposed dovecot socket
 
 Default: `12345`
 
+##### imap_host
+
+IMAP server hostname: address | address:port | [address]:port | imap.server.tld
+
+Default: `localhost`
+
+##### imap_security
+
+Secure the IMAP connection: tls | starttls | none
+
+Default: `tls`
+
 ##### lc_username
 
 Сonvert username to lowercase, must be true for case-insensitive auth

config

@@ -117,6 +117,14 @@
 # Port of via network exposed dovecot socket
 #dovecot_port = 12345
 
+# IMAP server hostname
+# Syntax: address | address:port | [address]:port | imap.server.tld
+#imap_host = localhost
+
+# Secure the IMAP connection
+# Value: tls | starttls | none
+#imap_security = tls
+
 # Htpasswd filename
 #htpasswd_filename = /etc/radicale/users