Login Process Proxying

Proxying using login processes is done for IMAP, POP3, Submission, and ManageSieve protocols.

LMTP and doveadm protocols implement their own proxying, but they try to be mostly compatible.

Proxying States

If login fails, the error message shows the connection state when the disconnection or timeout happened. For example timed out in state=login/banner with IMAP means that connection timed out while waiting for LOGIN command reply.

IMAP States

IMAP states are a bit more complicated. They describe both what commands the proxy has sent towards the backend and also what was the last received reply from the backend. The proxy can also send multiple commands pipelined, which are listed in the state.

For example the state could be capability+login/banner to mean that CAPABILITY and LOGIN commands have been sent, but only the IMAP banner reply has been received so far.

The list of sending states (left side of /):

States	Description
id	ID command used to send session ID and original IMAP client IP/port.
starttls	STARTTLS command.
capability	CAPABILITY command. Only used if backend doesn't send it automatically.
login	LOGIN command.
authenticate	AUTHENTICATE command. Sent if LOGIN command couldn't be used, e.g., because using master user login or non-cleartext authentication mechanism.
auth-continue	SASL continuation sent for AUTHENTICATE command.

The list of received states (right side of /):

States	Description
none	Nothing has been received so far.
banner	IMAP banner received ("* OK Dovecot ready").
id	ID command reply received.
starttls	STARTTLS command reply received.
capability	CAPABILITY command reply received.
auth-continue	AUTHENTICATE command asked for continuation (+ reply).
login	LOGIN or AUTHENTICATE command reply received.

POP3 States

POP3 states work a bit differently than IMAP states:

States	Description
banner	Nothing has been received so far (banner has NOT been received).
starttls	STLS command has been sent.
xclient	XCLIENT command has been sent.
login1	USER command has been sent.
login2	PASS or AUTH command has been sent.

Submission States

Submission states are similar to POP3:

States	Description
banner	Nothing has been received so far (banner has NOT been received).
ehlo	EHLO command has been sent.
starttls	STLS command has been sent.
tls-ehlo	EHLO command after STLS has been sent.
xclient	XCLIENT command has been sent.
authenticate	AUTH command has been sent.

ManageSieve States

States	Description
none	Nothing has been received so far.
tls-start	STARTTLS command has been sent.
tls-ready	STARTTLS command was accepted. TLS handshake was started.
xclient	XCLIENT command has been sent.
auth	AUTHENTICATE command has been sent.