Zimbra's IMAP server implementation question(s)
I’ve looked around for a while and can’t seem to locate a straight answer to what IMAP server is running under the hood. I’ve seen posts like “Zimbra comes with its own IMAP server.” …OK… so what does that mean? Is it a proprietary custom built IMAP server? It doesn’t appear to be dovecot or courier imap.
I see zimbra uses NGINX to proxy IMAP traffic:
NGINX Configuration Tips - Zimbra :: Wiki
Found the config file: /opt/zimbra/conf/nginx.conf.in
# NGINX POP/IMAP proxy configuration file for use with Zimbra
# Refer to nginx wiki at Main for configuration syntax
%%uncomment VAR:zimbraReverseProxyImapSaslGssapiEnabled%% imap_auth gssapi;
# Specify whether to use literal strings while issuing the LOGIN command
# to the upstream server. If set to on, then it means that NGINX will use
# literal strings to log in to the upstream server, and so the upstream
# MUST support literal strings
# If set to off, then NGINX uses quoted strings to log in to the upstream
# server when using the LOGIN command
# If not specified, imap_literalauth defaults to on
Wonder what the "upstream server" is....
"speaking" IMAP to the service running on zimbra doesn't provide much intel:
* OK mail.domainname.com Zimbra IMAP4rev1 service ready
. login email@example.com ******
. OK [CAPABILITY IMAP4rev1 ACL BINARY CATENATE CHILDREN CONDSTORE ENABLE ESEARCH ID IDLE LIST-EXTENDED LITERAL+ LOGIN-REFERRALS MULTIAPPEND NAMESPACE QRESYNC QUOTA RIGHTS=ektx SASL-IR SEARCHRES UIDPLUS UNSELECT WITHIN] LOGIN completed
. LIST "" "*"
* LIST (\NoInferiors) "/" "Junk"
* LIST (\HasNoChildren) "/" "Trash"
* LIST (\HasNoChildren) "/" "Contacts"
* LIST (\HasNoChildren) "/" "INBOX"
* LIST (\HasNoChildren) "/" "Emailed Contacts"
* LIST (\HasNoChildren) "/" "Drafts"
* LIST (\HasNoChildren) "/" "Chats"
* LIST (\HasNoChildren) "/" "Sent"
. OK LIST completed
. examine "INBOX"
* 0 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1] UIDs are valid for this mailbox
* OK [UIDNEXT 3] next expected UID is 3
* FLAGS (\Answered \Deleted \Draft \Flagged \Seen $Forwarded $MDNSent Forwarded $Junk $NotJunk Junk JunkRecorded NonJunk NotJunk)
* OK [PERMANENTFLAGS ()] junk-related flags are not permanent
* OK [HIGHESTMODSEQ 1] modseq tracked on this mailbox
. OK [READ-ONLY] EXAMINE completed
So what's "Zimbra IMAP4rev1"?
Thanks in advance!