<html><head></head><body><div>Daniel, as of 2.3.x, you have to <b>create a dh.pem parameter file</b> unless you can convert an existing parameter file:</div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span></b><a href="https://wiki.archlinux.org/index.php/dovecot#Generate_DH_parameters">https://wiki.archlinux.org/index.php/dovecot#Generate_DH_parameters</a></div><div><p style="margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><i><span class="Apple-tab-span" style="white-space:pre"> </span><span style="line-height: inherit;">To generate a new DH parameters file (this will take very long):</span></i></p><p style="margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><i><span style="line-height: inherit;"><span class="Apple-tab-span" style="white-space:pre"> </span></span></i><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><i># openssl dhparam -out /etc/dovecot/dh.pem 4096</i><p style="font-style: italic; margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><i style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"></i></p><p style="font-style: italic; margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><i style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><span class="Apple-tab-span" style="white-space:pre"> </span></i><i style="line-height: inherit;">then add the file to <code style="font-family: monospace; background-color: rgb(235, 241, 245); border: 0px solid rgb(234, 236, 240); border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; padding: 0px 0.3em; display: inline-block;">/etc/dovecot/conf.d/10-ssl.conf</code></i></p><p style="font-style: italic; margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><i style="line-height: inherit;"><code style="font-family: monospace; background-color: rgb(235, 241, 245); border: 0px solid rgb(234, 236, 240); border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; padding: 0px 0.3em; display: inline-block;"><span class="Apple-tab-span" style="white-space:pre"> </span></code></i><i style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;">ssl_dh = </etc/dovecot/dh.pem</i></p><p style="font-style: italic; margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><i style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><br></i></p><div><span style="line-height: 1.3em;">This creates a file dh.pem. </span><span style="line-height: inherit; font-family: sans-serif;">The dh.pem file contains the base </span><em style="line-height: inherit; font-family: sans-serif;">g</em><span style="line-height: inherit; font-family: sans-serif;"> and modulo </span><em style="line-height: inherit; font-family: sans-serif;">p</em><span style="line-height: inherit; font-family: sans-serif;">. These parameters define how OpenSSL performs the </span><a href="https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange" style="line-height: inherit; font-family: sans-serif;">Diffie-Hellman (DH) key-exchange</a><span style="line-height: inherit; font-family: sans-serif;">.</span></div><div><span style="line-height: 1.3em;"><br></span></div><div><span style="line-height: 1.3em;">More light reading:</span></div><div><span style="line-height: 1.3em;"><span class="Apple-tab-span" style="white-space:pre"> </span></span><a href="https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-english" style="font-family: sans-serif; line-height: inherit;">https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-english</a></div><div><span class="Apple-tab-span" style="white-space:pre"> </span><a href="https://security.stackexchange.com/questions/94390/whats-the-purpose-of-dh-parameters" style="font-family: sans-serif; line-height: inherit;">https://security.stackexchange.com/questions/94390/whats-the-purpose-of-dh-parameters</a></div></span><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><div><span style="line-height: 1.3em;"><span class="Apple-tab-span" style="white-space:pre"> </span></span></div><div><b>Yes</b> it took a very long time, indeed five hours in my case. But now it works.</div></span></p><div><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"></span><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><div style="color: rgb(34, 34, 34); font-size: 14px; line-height: 18.200000762939453px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);">I took a nap and listened to Messiah while it ground away...</div><div style="color: rgb(34, 34, 34); font-size: 14px; line-height: 18.200000762939453px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><br></div></span><div><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><div style="color: rgb(34, 34, 34); font-size: 14px; line-height: 18.200000762939453px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);">Enjoy...</div></span></div><p style="margin-top: 0.5em; margin-bottom: 0.5em; line-height: inherit; color: rgb(34, 34, 34); font-family: sans-serif; font-size: 14px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"></span><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"></span></p><span style="font-family: monospace; line-height: 1.3em; white-space: pre-wrap;"><div style="color: rgb(34, 34, 34); font-size: 14px; line-height: 18.200000762939453px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);">:-) </div><div style="color: rgb(34, 34, 34); font-size: 14px; line-height: 18.200000762939453px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><br></div><div style="color: rgb(34, 34, 34); font-size: 14px; line-height: 18.200000762939453px; orphans: 2; widows: 2; background-color: rgb(255, 255, 255);"><br></div></span></div></div><div>
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