Some protocols use a protocol-specific command to begin TLS negotiation (STARTTLS for SMTP and POP3), so stunnel needs to know how (and be told) to use that command.
However, I believe you only need to do this if using TLS on a POP3 connection on port 110. POP3S on port 995 should implicitly use TLS.
*Andrew Culver* System Engineer Western Technology Services https://wts.uwo.ca University of Western Ontario https://www.uwo.ca e: aculver@uwo.ca p: 519-661-2111 x80265 <15196612111,80265> cal: html http://goo.gl/wVoDlo | ics http://goo.gl/ncUjV0
On Thu, Jan 18, 2018 at 9:51 AM, peter@easthope.ca wrote:
P.s.
From: "Phil Smith III" phs3stuff@cox.net Date: Wed, 17 Jan 2018 21:59:42 -0500
protocol = pop3
The stunnel(8) manual has this. "protocol = PROTO application protocol to negotiate TLS This option enables initial, protocol-specific negotiation of the TLS encryption."
Is there any need for protocol-specific negotiation? Why? Stunnel provides a tunnel and POP3 works inside. That's all. Try the configuration without the protocol option.
Regards, ... Peter E.
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