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I've got a Postfix with Courier IMAP mail server mostly set up. IMAP authentication works as expected on port 143 (when SSL is disabled), but whenever SSL is enabled or port 993 is used, nothing happens.

Literally, the server sends no data:

openssl s_client -connect localhost:993

CONNECTED(00000003)
write:errno=104
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 317 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
---

I've made sure that TLS_CERTFILE, specified in /etc/courier/imapd-ssl, exists and is referenced correctly.

I've also made sure IMAPDSSLSTART=1 and IMAPDSTARTTLS=YES.

I'm at a loss...

grekasius
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TheToolBox
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1 Answers1

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To properly test the STARTTLS feature, you need to use the following command:

openssl s_client -connect localhost:993 -startls imap

Without that -starttls option, you are not actually testing the encryption. From what info you have here it's wouldn't be clear whether you have a proper encryption setup.

OpenSSL can also be used to verify a specific version by adding an option such as -tls1_2 to the command line. The connection will fail if the server doesn't support that specific version.

Alexis Wilke
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