<story><title>Email: Explained from first principles</title><url>https://explained-from-first-principles.com/email/</url></story><parent_chain><item><author>layer8</author><text>I love such thorough expositions, although it isn’t quite as thorough as I would like. Two examples that caught my attention in the parts I read:&lt;p&gt;1. It doesn’t mention the old convention for writing an email address with display name as&lt;p&gt;&lt;pre&gt;&lt;code&gt;  john.doe@example.net (John Doe)
&lt;/code&gt;&lt;/pre&gt;
instead of:&lt;p&gt;&lt;pre&gt;&lt;code&gt;  John Doe &amp;lt;john.doe@example.net&amp;gt;
&lt;/code&gt;&lt;/pre&gt;
2. It states that subject prefixes like “Re:” have no technical relevance. That’s not entirely true, because email clients recognize existing prefixes when replying&amp;#x2F;forwarding, in order to not add a redundant one. There are several issues here:&lt;p&gt;- Localized email software sometimes uses a different prefix than “Re”, based on the local language. This is an issue when having an email thread between email clients who don’t recognize each other’s local-language prefixes. (Arguably, it would be better for everyone to stick with “Re” regardless of  language.)&lt;p&gt;- Some email clients have the convention of adding a count to the “Re”, e.g. “Re[2]:”, “Re[3]:”, and so on. When you write an email client, you may want to consider recognizing those.&lt;p&gt;Due to the variety in subject prefixes, some email clients allow users to configure a regex.</text></item></parent_chain><comment><author>KasparEtter</author><text>Hi layer8, thanks for the feedback! I must say that your standards for thoroughness are pretty high.  Since I claimed at the very top that my article covers all aspects of modern email, I don&amp;#x27;t mind your criticism at all.&lt;p&gt;I haven&amp;#x27;t thought about the prefix chaining issue, and I&amp;#x27;m happy to mention this in a future revision of the article. I would still argue that this is below a reasonable level of technical significance as neither conversation grouping nor message delivery is affected by it. It&amp;#x27;s more like displaying &amp;quot;(No subject)&amp;quot; instead of actually displaying no subject.&lt;p&gt;Do you have any source for what you say is an old display name convention? I&amp;#x27;ve just checked the standards, and as far as I can tell after a quick glance, RFC 822 (&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;datatracker.ietf.org&amp;#x2F;doc&amp;#x2F;html&amp;#x2F;rfc822#section-6&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;datatracker.ietf.org&amp;#x2F;doc&amp;#x2F;html&amp;#x2F;rfc822#section-6&lt;/a&gt;) doesn&amp;#x27;t mention display names at all, and its successor RFC 2822 (&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;datatracker.ietf.org&amp;#x2F;doc&amp;#x2F;html&amp;#x2F;rfc2822#section-3.4&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;datatracker.ietf.org&amp;#x2F;doc&amp;#x2F;html&amp;#x2F;rfc2822#section-3.4&lt;/a&gt;) mentions display names only with angle brackets.&lt;p&gt;PS: I have quite a few topics on my todo list, which I should add in a future revision of the article in order to live up to the claim of covering all aspects of modern email. These include MAPI, Microsoft&amp;#x27;s autodiscover mechanism, direct mailbox addressing, domain-to-domain encryption, and link rewriting in incoming mails. Some information is also no longer up to date by now.</text></comment>
<story><title>Email: Explained from first principles</title><url>https://explained-from-first-principles.com/email/</url></story><parent_chain><item><author>layer8</author><text>I love such thorough expositions, although it isn’t quite as thorough as I would like. Two examples that caught my attention in the parts I read:&lt;p&gt;1. It doesn’t mention the old convention for writing an email address with display name as&lt;p&gt;&lt;pre&gt;&lt;code&gt;  john.doe@example.net (John Doe)
&lt;/code&gt;&lt;/pre&gt;
instead of:&lt;p&gt;&lt;pre&gt;&lt;code&gt;  John Doe &amp;lt;john.doe@example.net&amp;gt;
&lt;/code&gt;&lt;/pre&gt;
2. It states that subject prefixes like “Re:” have no technical relevance. That’s not entirely true, because email clients recognize existing prefixes when replying&amp;#x2F;forwarding, in order to not add a redundant one. There are several issues here:&lt;p&gt;- Localized email software sometimes uses a different prefix than “Re”, based on the local language. This is an issue when having an email thread between email clients who don’t recognize each other’s local-language prefixes. (Arguably, it would be better for everyone to stick with “Re” regardless of  language.)&lt;p&gt;- Some email clients have the convention of adding a count to the “Re”, e.g. “Re[2]:”, “Re[3]:”, and so on. When you write an email client, you may want to consider recognizing those.&lt;p&gt;Due to the variety in subject prefixes, some email clients allow users to configure a regex.</text></item></parent_chain><comment><author>sbuk</author><text>Email clients don’t really have a spec to follow other than parsing messages that are received via POP or more likely IMAP these days (not forgetting MAPI either). Adding FWD or RE to a subject field doesn’t appear anywhere in the email message RFCs, starting with 822. As such they are undocumented conventions or extensions to the specs, and as the article points out technically irrelevant - no MDAs, MTAs or MUAs that do not “support” features that utilise these conventions will fail to parse a message.</text></comment>