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23 Setting up my personal mailserver
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39 <p> 2019-08-15 </p>
40 <h1> Setting up my personal mailserver </h1>
41 <h2> This is probably a terrible idea… </h2>
42 <p>A mailserver was a long time coming. I’d made an attempt at setting one up
43around ~4 years ago (ish), and IIRC, I quit when it came to DNS. And
44I almost did this time too.<sup class="footnote-ref" id="fnref-1"><a href="#fn-1">1</a></sup></p>
45
46<p>For this attempt, I wanted a simpler approach. I recall how terribly
47confusing Dovecot & Postfix were to configure and hence I decided to look
48for a containerized solution, that most importantly, runs on my cheap $5
49Digital Ocean VPS — 1 vCPU and 1 GB memory. Of which only around 500 MB
50is actually available. So yeah, <em>pretty</em> tight.</p>
51
52<h3 id="whats-available">What’s available</h3>
53
54<p>Turns out, there are quite a few of these OOTB, ready to deply solutions.
55These are the ones I came across:</p>
56
57<ul>
58<li><p><a href="https://poste.io">poste.io</a>: Based on an “open core” model. The base install is open source
59and free (as in beer), but you’ll have to pay for the extra stuff.</p></li>
60<li><p><a href="https://mailu.io">mailu.io</a>: Free software. Draws inspiration from poste.io,
61but ships with a web UI that I didn’t need. </p></li>
62<li><p><a href="https://mailcow.email">mailcow.email</a>: These fancy domains are getting ridiculous. But more importantly
63they need 2 GiB of RAM <em>plus</em> swap?! Nope.</p></li>
64<li><p><a href="https://mailinabox.email">Mail-in-a-Box</a>: Unlike the ones above, not a Docker-based solution but definitely worth
65a mention. It however, needs a fresh box to work with. A box with absolutely
66nothing else on it. I can’t afford to do that.</p></li>
67<li><p><a href="https://github.com/tomav/docker-mailserver/">docker-mailserver</a>: <strong>The winner</strong>. </p></li>
68</ul>
69
70<h3 id="so-docker-mailserver">So… <code>docker-mailserver</code></h3>
71
72<p>The first thing that caught my eye in the README:</p>
73
74<blockquote>
75 <p>Recommended:</p>
76
77 <ul>
78 <li>1 CPU</li>
79 <li>1GB RAM</li>
80 </ul>
81
82 <p>Minimum:</p>
83
84 <ul>
85 <li>1 CPU</li>
86 <li>512MB RAM</li>
87 </ul>
88</blockquote>
89
90<p>Fantastic, I can somehow squeeze this into my existing VPS.
91Setup was fairly simple & the docs are pretty good. Especially the single
92<code>.env</code> file for configuration, which is great.
93However, I did run into a couple of hiccups here and there.</p>
94
95<p>One especially nasty one was <code>docker</code> / <code>docker-compose</code> running out
96of memory.</p>
97
98<pre><code>Error response from daemon: cannot stop container: 2377e5c0b456: Cannot kill container 2377e5c0b456226ecaa66a5ac18071fc5885b8a9912feeefb07593638b9a40d1: OCI runtime state failed: runc did not terminate sucessfully: fatal error: runtime: out of memory
99</code></pre>
100
101<p>But it eventually worked after a couple of attempts.</p>
102
103<p>The next thing I struggled with — DNS. Especially with the step where
104the DKIM keys are generated<sup class="footnote-ref" id="fnref-2"><a href="#fn-2">2</a></sup>. The output under <code>config/opendkim/keys/domain.tld/mail.txt</code>
105isn’t exactly CloudFlare friendly; they can’t be directly copy-pasted into
106a <code>TXT</code> record. </p>
107
108<p>This is what it looks like.</p>
109
110<pre><code>mail._domainkey IN TXT ( "v=DKIM1; h=sha256; k=rsa; "
111 "p=<key>"
112 "<more key>" ) ; ----- DKIM key mail for icyphox.sh
113</code></pre>
114
115<p>But while configuring the record, you set “Type” to <code>TXT</code>, “Name” to <code>mail._domainkey</code>,
116and the “Value” to what’s inside the parenthesis <code>( )</code>, <em>removing</em> the quotes <code>""</code>.
117Also remove the part that appears to be a comment <code>; ----- ...</code>.</p>
118
119<p>To simplify debugging DNS issues later, it’s probably a good idea to
120point to your mailserver using a subdomain like <code>mail.domain.tld</code> using an
121<code>A</code> record.
122You’ll then have to set an <code>MX</code> record with the “Name” as <code>@</code> (or whatever your DNS provider
123uses to denote the root domain) and the “Value” to <code>mail.domain.tld</code>.
124And finally, the <code>PTR</code> (pointer record, I think), which is the reverse of
125your <code>A</code> record — “Name” as the server IP and “Value” as <code>mail.domain.tld</code>.
126I learnt this part the hard way, when my outgoing email kept getting
127rejected by Tutanota’s servers.</p>
128
129<p>Yet another hurdle — SSL/TLS certificates. This isn’t very properly
130documented, unless you read through the <a href="https://github.com/tomav/docker-mailserver/wiki/Installation-Examples">wiki</a>
131and look at an example. In short, install <code>certbot</code>, have port 80 free,
132and run <code>certbot certonly --standalone -d mail.domain.tld</code>. Once that’s
133done, edit the <code>docker-compose.yml</code> file to mount <code>/etc/letsencrypt</code> in
134the container, something like so:</p>
135
136<div class="codehilite"><pre><span></span><code><span class="nn">...</span>
137
138<span class="nt">volumes</span><span class="p">:</span>
139 <span class="p p-Indicator">-</span> <span class="l l-Scalar l-Scalar-Plain">maildata:/var/mail</span>
140 <span class="p p-Indicator">-</span> <span class="l l-Scalar l-Scalar-Plain">mailstate:/var/mail-state</span>
141 <span class="p p-Indicator">-</span> <span class="l l-Scalar l-Scalar-Plain">./config/:/tmp/docker-mailserver/</span>
142 <span class="p p-Indicator">-</span> <span class="l l-Scalar l-Scalar-Plain">/etc/letsencrypt:/etc/letsencrypt</span>
143
144<span class="nn">...</span>
145</code></pre></div>
146
147<p>With this done, you shouldn’t have mail clients complaining about
148wonky certs for which you’ll have to add an exception manually.</p>
149
150<h3 id="why-would-you">Why would you…?</h3>
151
152<p>There are a few good reasons for this:</p>
153
154<h4 id="privacy">Privacy</h4>
155
156<p>No really, this is <em>the</em> best choice for truly private
157email. Not ProtonMail, not Tutanota. Sure, they claim so and I don’t
158dispute it. Quoting Drew Devault<sup class="footnote-ref" id="fnref-3"><a href="#fn-3">3</a></sup>,</p>
159
160<blockquote>
161 <p>Truly secure systems do not require you to trust the service provider.</p>
162</blockquote>
163
164<p>But you have to <em>trust</em> ProtonMail. They run open source software, but
165how can you really be sure that it isn’t a backdoored version of it?</p>
166
167<p>When you host your own mailserver, you truly own your email without having to rely on any
168third-party.
169This isn’t an attempt to spread FUD. In the end, it all depends on your
170threat model™.</p>
171
172<h4 id="decentralization">Decentralization</h4>
173
174<p>Email today is basically run by Google. Gmail has over 1.2 <em>billion</em>
175active users. That’s obscene.
176Email was designed to be decentralized but big corps swooped in and
177made it a product. They now control your data, and it isn’t unknown that
178Google reads your mail. This again loops back to my previous point, privacy.
179Decentralization guarantees privacy. When you control your mail, you subsequently
180control who reads it.</p>
181
182<h4 id="personalization">Personalization</h4>
183
184<p>Can’t ignore this one. It’s cool to have a custom email address to flex.</p>
185
186<p><code>x@icyphox.sh</code> vs <code>gabe.newell4321@gmail.com</code></p>
187
188<p>Pfft, this is no competition.</p>
189
190<div class="footnotes">
191<hr />
192<ol>
193<li id="fn-1">
194<p>My <a href="https://twitter.com/icyphox/status/1161648321548566528">tweet</a> of frustration. <a href="#fnref-1" class="footnoteBackLink" title="Jump back to footnote 1 in the text.">↩</a></p>
195</li>
196
197<li id="fn-2">
198<p><a href="https://github.com/tomav/docker-mailserver#generate-dkim-keys">Link</a> to step in the docs. <a href="#fnref-2" class="footnoteBackLink" title="Jump back to footnote 2 in the text.">↩</a></p>
199</li>
200
201<li id="fn-3">
202<p>From his <a href="https://drewdevault.com/2018/08/08/Signal.html">article</a> on why he doesn’t trust Signal. <a href="#fnref-3" class="footnoteBackLink" title="Jump back to footnote 3 in the text.">↩</a></p>
203</li>
204</ol>
205</div>
206
207 </div>
208 <hr />
209 <p class="muted">Questions or comments? Open an issue at <a href="https://github.com/icyphox/site">this repo</a>, or send a plain-text email to <a href="mailto:x@icyphox.sh">x@icyphox.sh</a>.</p>
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