OK, so still struggling. Tried installing Mercury 4.80 on a old Windows 7 machine, and the certificate generation works!  I created a CSR using this copy, revoked my certificate, and requested a new one using the CSR.  I compiled them into a single file (PRIVATE KEY and CERTIFICATE), as I gather you're supposed to do.  Now I'm getting a new error, seems to make 2 session logs when I attempt to connect.  Any hints?
 
12:59:56.261: --- 14 Jan 2019, 12:59:56.261 ---
12:59:56.261: Accepted connection from 'xxx.xxx.xxx.xxx', timeout 120 seconds.
12:59:56.266: Connection from xxx.xxx.xxx.xxx, Mon, 14 Jan 2019 12:59<cr><lf>
12:59:56.266: << * OK d IMAP4rev1 Mercury/32 v4.80.145 server ready.<cr><lf>
12:59:56.331: >> 1 CAPABILITY<cr><lf>
12:59:56.331: << * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED X-MERCURY-1<cr><lf>
12:59:56.331: << 1 OK CAPABILITY complete.<cr><lf>
12:59:56.391: >> 2 STARTTLS<cr><lf>
12:59:56.391: << 2 OK Begin SSL/TLS negotiation now.<cr><lf>
-Then- 
 
12:59:56.651: --- 14 Jan 2019, 12:59:56.651 ---
12:59:56.651: Accepted connection from 'xxx.xxx.xxx.xxx', timeout 120 seconds.
12:59:56.656: Connection from xxx.xxx.xxx.xxx, Mon, 14 Jan 2019 12:59<cr><lf>
12:59:56.656: << * OK d IMAP4rev1 Mercury/32 v4.80.145 server ready.<cr><lf>
12:59:56.661: >> 
12:59:56.666: << * BAD Malformed command or oversize literal.<cr><lf>
12:59:56.666: >> ÀÀ
12:59:56.666: << * BAD Malformed command or oversize literal.<cr><lf>
12:59:56.666: >> retson.net
12:59:56.666: << * BAD Malformed command or oversize literal.<cr><lf>
12:59:56.726: 7: Socket read error 10054 (connection aborted by remote host)
12:59:56.731: --- Connection closed normally at 14 Jan 2019, 12:59:56.731. ---
12:59:56.731: 
 
OK, so still struggling. Tried installing Mercury 4.80 on a old Windows 7 machine, and the certificate generation works!&nbsp; I created a CSR using this copy, revoked my certificate, and requested a new one using the CSR.&nbsp; I compiled them into a single file (PRIVATE KEY and CERTIFICATE), as I gather you're supposed to do.&nbsp; Now I'm getting a new error, seems to make 2 session logs when I attempt to connect.&nbsp; Any hints?
<div><span style="font-size: 10pt;">&nbsp;</span></div><div>12:59:56.261: --- 14 Jan 2019, 12:59:56.261 ---</div><div>12:59:56.261: Accepted connection from 'xxx.xxx.xxx.xxx', timeout 120 seconds.</div><div>12:59:56.266: Connection from xxx.xxx.xxx.xxx, Mon, 14 Jan 2019 12:59&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.266: &lt;&lt; * OK d IMAP4rev1 Mercury/32 v4.80.145 server ready.&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.331: &gt;&gt; 1 CAPABILITY&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.331: &lt;&lt; * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED X-MERCURY-1&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.331: &lt;&lt; 1 OK CAPABILITY complete.&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.391: &gt;&gt; 2 STARTTLS&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.391: &lt;&lt; 2 OK Begin SSL/TLS negotiation now.&lt;cr&gt;&lt;lf&gt;</div><div>
</div><div>-Then-&nbsp;</div><div>&nbsp;</div><div>12:59:56.651: --- 14 Jan 2019, 12:59:56.651 ---</div><div>12:59:56.651: Accepted connection from 'xxx.xxx.xxx.xxx', timeout 120 seconds.</div><div>12:59:56.656: Connection from xxx.xxx.xxx.xxx, Mon, 14 Jan 2019 12:59&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.656: &lt;&lt; * OK d IMAP4rev1 Mercury/32 v4.80.145 server ready.&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.661: &gt;&gt; </div><div>12:59:56.666: &lt;&lt; * BAD Malformed command or oversize literal.&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.666: &gt;&gt; ÀÀ</div><div>12:59:56.666: &lt;&lt; * BAD Malformed command or oversize literal.&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.666: &gt;&gt; retson.net</div><div>12:59:56.666: &lt;&lt; * BAD Malformed command or oversize literal.&lt;cr&gt;&lt;lf&gt;</div><div>12:59:56.726: 7: Socket read error 10054 (connection aborted by remote host)</div><div>12:59:56.731: --- Connection closed normally at 14 Jan 2019, 12:59:56.731. ---</div><div>12:59:56.731:&nbsp;</div><div>&nbsp;</div>