dovecot - May 2016 - Cannot connect to Dovecot IMAP or POP

> 	   	2. openssl s_client -connect mail.privustech.com:xxx
>   		a. xxx=25, 110, 143 all return
>   			error:140770FC
You need to add the "-starttls protocol" parameter, otherwise
"openssl s_client"
thinks your using SSL, not STARTTLS i.e.

 	openssl s_client -starttls pop3 -connect mail.privustech.com:110
 	openssl s_client -starttls imap -connect mail.privustech.com:143

But even if you do that, you get the same error because it can't start the
TLS session:

 	$ nc mail.privustech.com 143
 	* OK [CAPABILITY IMAP4REV1 I18NLEVEL=1 LITERAL+ SASL-IR LOGIN-REFERRALS
STARTTLS LOGINDISABLED AUTH=CRAM-MD5] privustech.com IMAP4rev1 2007e.404 at Wed,
4 May 2016 22:26:36 -0400 (EDT)
 	x STARTTLS
 	x NO Server certificate not installed

So there you go, dovecot can't get at your server certificate.  You can
start the search of your problem from there.  The configuration

 	verbose_ssl = yes

will help to log the problem.
>                       ssl_dh_parameters_length = 2048
Probably not related to your problem, but this will cause wildly variable
dovecot initialization times, as temp key generation of this  length
can result in a lot of candidate primailty testing.

Joseph Tam <jtam.home at gmail.com>

>                       ssl_dh_parameters_length = 2048
> 
> Probably not related to your problem, but this will cause wildly variable
> dovecot initialization times, as temp key generation of this  length
> can result in a lot of candidate primailty testing.
> 
The key generation is done once and stored to disk. Then reused until eternity.

---
Aki Tuomi