blocks|key|4206872|text|电子邮件地址不得超过254个字符。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|4206873|这被submitted+erratum之后的IETF所接受。任何给定地址的完整诊断都可以通过online获得。RFC3696的原始版本将320描述为最大长度，但是John+Klensin随后接受了一个错误的值，因为路径被定义为|4206874|Path+=+"<"+[+A-d-l+":"+]+Mailbox+">"|code-block|syntax|javascript|4206875|因此，Mailbox元素(即电子邮件地址)前后有尖括号以形成路径，该路径的最大长度为254个字符，将路径长度限制为256个字符或更少。|4206876|在RFC+5321状态中指定的最大长度：|4206877|4206878|反向路径或正向路径的最大总长度为256个字符。|blockquote|4206879|4206880|4206881|RFC3696被修正为here。|4206882|人们应该特别注意errata+against+RFC+3696。规范示例中有三个实际上是无效地址。|4206883|我整理了几百个测试地址，你可以在http://www.dominicsayers.com/isemail上找到|4206884|entityMap|0|LINK|mutability|MUTABLE|url|http://www.rfc-editor.org/errata_search.php?rfc=3696&eid=1690|1|http://isemail.info/|2|https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3|3|http://www.rfc-editor.org/errata_search.php?rfc=3696|4|5|http://www.dominicsayers.com/isemail^0|A|4|0|2|H|0|1A|6|1|0|0|0|1|8|2|0|0|0|0|0|B|4|3|0|8|N|4|0|G|10|5|0^^$0|@$1|2|3|4|5|6|7|1J|8|@$9|1K|A|1L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1M|8|@]|D|@$9|1N|A|1O|1|1P]|$9|1Q|A|1R|1|1S]]|E|$]]|$1|H|3|I|5|J|7|1T|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1U|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1V|8|@]|D|@$9|1W|A|1X|1|1Y]]|E|$]]|$1|Q|3|-4|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|R|3|S|5|T|7|20|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|21|8|@]|D|@]|E|$]]|$1|V|3|-4|5|6|7|22|8|@]|D|@]|E|$]]|$1|W|3|X|5|6|7|23|8|@]|D|@$9|24|A|25|1|26]]|E|$]]|$1|Y|3|Z|5|6|7|27|8|@]|D|@$9|28|A|29|1|2A]]|E|$]]|$1|10|3|11|5|6|7|2B|8|@]|D|@$9|2C|A|2D|1|2E]]|E|$]]|$1|12|3|-4|5|6|7|2F|8|@]|D|@]|E|$]]]|13|$14|$5|15|16|17|E|$18|19]]|1A|$5|15|16|17|E|$18|1B]]|1C|$5|15|16|17|E|$18|1D]]|1E|$5|15|16|17|E|$18|1F]]|1G|$5|15|16|17|E|$18|1F]]|1H|$5|15|16|17|E|$18|1I]]]]

An email address must not exceed 254 characters.
This was accepted by the IETF following <a href="http://www.rfc-editor.org/errata_search.php?rfc=3696&amp;eid=1690" rel="noreferrer">submitted erratum</a>. A full diagnosis of any given address is available <a href="http://isemail.info/" rel="noreferrer">online</a>. The original version of RFC 3696 described 320 as the maximum length, but John Klensin subsequently accepted an incorrect value, since a Path is defined as
<pre><code>Path = &quot;&lt;&quot; [ A-d-l &quot;:&quot; ] Mailbox &quot;&gt;&quot;
</code></pre>
So the Mailbox element (i.e., the email address) has angle brackets around it to form a Path, which a maximum length of 254 characters to restrict the Path length to 256 characters or fewer.
The maximum length specified in <a href="https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3" rel="noreferrer">RFC 5321</a> states:
<blockquote>
The maximum total length of a reverse-path or forward-path is 256 characters.
</blockquote>
RFC 3696 was corrected <a href="http://www.rfc-editor.org/errata_search.php?rfc=3696" rel="noreferrer">here</a>.
People should be aware of the <a href="http://www.rfc-editor.org/errata_search.php?rfc=3696" rel="noreferrer">errata against RFC 3696</a> in particular. Three of the canonical examples are in fact invalid addresses.
I've collated a couple hundred test addresses, which you can find at <a href="http://www.dominicsayers.com/isemail" rel="noreferrer">http://www.dominicsayers.com/isemail</a>

blocks|key|3360808|text|320|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3360809|这些线段看起来像这样|3360810|{64}@{255}|3360811|64+%2B1%2B+255+=+320|3360812|如果你正在验证电子邮件，你也应该阅读这篇文章：I+Knew+How+To+Validate+An+Email+Address+Until+I+Read+The+RFC|offset|length|3360813|entityMap|0|LINK|mutability|MUTABLE|url|https://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx/^0|0|0|0|0|N|1O|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|X|8|@]|9|@$J|Y|K|Z|1|10]]|A|$]]|$1|L|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|S]]]]

320
And the segments look like this
{64}@{255}
64 + 1 + 255 = 320
You should also read this if you are validating emails: <a href="https://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx/" rel="noreferrer">I Knew How To Validate An Email Address Until I Read The RFC</a>

blocks|key|938794|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|938795|+user|blockquote|offset|length|style|BOLD|938796|938797|用户名的最大总长度为64个字符。|938798|域|938799|域名部分(@后面的域名部分)最多255个字符|938800|938801|但是，++的读取有一个限制：|938802|938803|反向路径或正向路径的最大总长度为256个字符，包括标点符号和元素分隔符“。由于不适合这些字段的地址通常不有用，因此地址长度的上限通常应视为256，但路径定义为:+path+=“<”A-d-l“：”Mailbox“>”除了邮箱，正向路径还将包含至少一对尖括号，这将电子邮件地址限制为254个字符。|938804|938805|entityMap^0|0|1|4|0|0|0|0|1|0|0|0|0|3|5|9|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|X|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|Y|7|@$D|Z|E|10|F|G]]|8|@]|9|$]]|$1|H|3|-4|4|5|6|11|7|@]|8|@]|9|$]]|$1|I|3|J|4|5|6|12|7|@]|8|@]|9|$]]|$1|K|3|L|4|5|6|13|7|@$D|14|E|15|F|G]]|8|@]|9|$]]|$1|M|3|N|4|5|6|16|7|@]|8|@]|9|$]]|$1|O|3|-4|4|5|6|17|7|@]|8|@]|9|$]]|$1|P|3|Q|4|5|6|18|7|@$D|19|E|1A|F|G]|$D|1B|E|1C|F|G]]|8|@]|9|$]]|$1|R|3|-4|4|5|6|1D|7|@]|8|@]|9|$]]|$1|S|3|T|4|C|6|1E|7|@]|8|@]|9|$]]|$1|U|3|-4|4|5|6|1F|7|@]|8|@]|9|$]]|$1|V|3|-4|4|5|6|1G|7|@]|8|@]|9|$]]]|W|$]]

<blockquote>
 user
 
 The maximum total length of a user name is 64 characters.
 
 domain
 
 Maximum of 255 characters in the domain part (the one after the “@”)
</blockquote>

However, there is a restriction in <a href="https://www.ietf.org/rfc/rfc2821.txt" rel="noreferrer">RFC 2821</a> reading: 

<blockquote>
 The maximum total length of a reverse-path or forward-path is 256
 characters, including the punctuation and element separators”. Since
 addresses that don’t fit in those fields are not normally useful, the
 upper limit on address lengths should normally be considered to be
 256, but a path is defined as: Path = “&lt;” [ A-d-l “:” ] Mailbox “>”
 The forward-path will contain at least a pair of angle brackets in
 addition to the Mailbox, which limits the email address to 254
 characters.
</blockquote>

blocks|key|934033|text|为了帮助像我这样困惑的新手，答案是“有效电子邮件地址的最大长度是多少？”是254个字符的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|934034|如果您的应用程序使用电子邮件，只需将您的字段设置为接受254个字符或更少，就可以了。|934035|你可以在一封电子邮件上运行一系列测试，看看它在这里是否有效。http://isemail.info/|934036|RFC或请求注解是互联网工程任务组(IETF)的一种出版物，它将254个字符定义为限制。位于此处-+https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3|934037|entityMap|0|LINK|mutability|MUTABLE|url|http://isemail.info/|1|https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3^0|11|7|0|0|U|K|0|0|1E|1G|1|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@$9|10|A|11|1|12]]|E|$]]|$1|J|3|K|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|L|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S]]|T|$5|O|P|Q|E|$R|U]]]]

To help the confused rookies like me, the answer to &quot;What is the maximum length of a valid email address?&quot; is 254 characters.
If your application uses an email, just set your field to accept 254 characters or less and you are good to go.
You can run a bunch of tests on an email to see if it is valid here. <a href="http://isemail.info/" rel="nofollow noreferrer">http://isemail.info/</a>
The RFC, or Request for Comments is a type of publication from the Internet Engineering Task Force (IETF) that defines 254 characters as the limit. Located here - <a href="https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3" rel="nofollow noreferrer">https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3</a>

blocks|key|3361042|text|根据下面的文章：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3361043|https://www.rfc-editor.org/rfc/rfc3696+(第6页，Section+3)|offset|length|3361044|其中提到：|3361045|3361046|“电子邮件地址有长度限制。该限制在”本地“部分(在”@“之前)最多为64个字符(八位字节)，在域部分(在”@“之后)最多为255个字符(八位字节)，总长度为320个字符。处理电子邮件的系统应准备好处理这么长的地址，即使它们很少遇到。”|blockquote|3361047|3361048|3361049|因此，一个电子邮件地址的最大总长度为320个字符(“本地部分”：64+%2B+"@"：1%2B“域部分”：255，总和为320)|3361050|entityMap|0|LINK|mutability|MUTABLE|url|https://www.rfc-editor.org/rfc/rfc3696|1|https://www.rfc-editor.org/rfc/rfc3696#section-3^0|0|0|12|0|18|9|1|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|10|8|@]|9|@$D|11|E|12|1|13]|$D|14|E|15|1|16]]|A|$]]|$1|F|3|G|5|6|7|17|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|18|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|19|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1C|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]|X|$5|S|T|U|A|$V|Y]]]]

According to the below article:
<a href="https://www.rfc-editor.org/rfc/rfc3696" rel="nofollow noreferrer">https://www.rfc-editor.org/rfc/rfc3696</a> (Page 6, <a href="https://www.rfc-editor.org/rfc/rfc3696#section-3" rel="nofollow noreferrer">Section 3</a>)
It's mentioned that:
<blockquote>
&quot;There is a length limit on
email addresses. That limit is a maximum of 64 characters (octets)
in the &quot;local part&quot; (before the &quot;@&quot;) and a maximum of 255 characters
(octets) in the domain part (after the &quot;@&quot;) for a total length of 320
characters. Systems that handle email should be prepared to process
addresses which are that long, even though they are rarely
encountered.&quot;
</blockquote>
So, the maximum total length for an email address is 320 characters
(&quot;local part&quot;: 64 + &quot;@&quot;: 1 + &quot;domain part&quot;: 255 which sums to 320)

blocks|key|3361106|text|另一个答案有点让水变得浑浊了。简单的答案:在我们的email+256控件中，总共有254个字符代表整个电子邮件地址，包括开头的隐含的"<“和结尾的">”。因此，剩下的254个供我们使用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3361107|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The other answers muddy the water a bit. 
Simple answer: 254 total chars in our control for email
256 are for the ENTIRE email address, which includes implied "&lt;" at the beginning, and ">" at the end. Therefore, 254 are left over for our use.

blocks|key|143667|text|TLDR应答|type|unstyled|depth|inlineStyleRanges|entityRanges|data|143668|给出一个电子邮件地址，比如...|143669|me@example.com|code-block|syntax|javascript|143670|长度限制如下：|143671|整个电子邮件地址(也称为“|143672|”)：即me@example.com+--最大字符数，即me+--+256+character+maximum.|unordered-list-item|offset|length|style|CODE|143673|Local-Part：，即，example.com+--+254+characters+|143674|。|143675|143676|143677|来源-+TLDR；|143678|RFC标准在不断发展，但如果您希望在一行中包含2009年的IETF源代码：|143679|地址长度的|143680|+...the上限通常应视为256。(来源：。)|blockquote|143681|143682|143683|来源-历史|143684|SMTP最初在1982年8月发布的RFC821中定义了什么是路径，它是an+official+Internet+Standard+(大多数RFC只是建议)。引用它..。|143685|143686|+...a反向路径，指定邮件发件人。|143687|143688|...a转发路径，指定邮件的收件人。|143689|143690|2001年4月发布的RFC2821是过时的标准，它定义了我们当前本地部分、域和路径的最大值。2008年10月发布的新标准草案RFC5321保持了同样的限制。在这两个日期之间，RFC3696于2004年2月发布。它错误地将最大电子邮件地址限制引用为320-characters，但本文仅供参考，并表示：“本备忘录为互联网社区提供信息。它没有指定任何类型的互联网标准。”所以，我们可以忽略它。|143691|引用RFC5321中确认的现代公认标准RFC2821+...|143692|143693|+4.5.3.1.1。本地-部分|BOLD|143694|143695|用户名或其他本地部分的最大总长度为64个字符。|143696|4.5.3.1.2。域|143697|域名或数字的最大总长度为255个字符。|143698|4.5.3.1.3。路径|143699|反向路径或正向路径的最大总长度为256个字符(包括标点符号和元素分隔符)。|143700|143701|您会注意到，我表示的域最大值为254，而RFC表示域的最大值为255。这是一个简单的算术问题。255个字符的域加上"@“符号是256个字符的路径，这是最大路径长度。但是，空名是无效的，因此该域实际上最多有254个域名。|143702|entityMap|0|LINK|mutability|MUTABLE|url|https://www.rfc-editor.org/rfc/rfc821|1|https://en.wikipedia.org/wiki/Internet_Standard#:%257E:text=The%2520IETF%2520also%2520defines%2520a,prior%2520to%2520an%2520Internet%2520Standard.|2|https://www.rfc-editor.org/rfc/rfc2821|3|https://www.rfc-editor.org/rfc/rfc5321|4|https://www.rfc-editor.org/rfc/rfc3696^0|0|0|0|0|0|Y|3|0|T|3|1|1|0|0|0|0|0|0|0|0|0|H|6|0|Z|T|1|0|0|0|0|0|0|3F|3|A|7|2|1Q|7|3|2F|7|4|0|0|0|1|F|0|0|0|0|B|0|0|0|C|0|0|0|0^^$0|@$1|2|3|4|5|6|7|2N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|2O|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|2P|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|2Q|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|2R|8|@]|9|@]|A|$]]|$1|M|3|N|5|O|7|2S|8|@$P|2T|Q|2U|R|S]]|9|@]|A|$]]|$1|T|3|U|5|O|7|2V|8|@$P|2W|Q|2X|R|S]]|9|@]|A|$]]|$1|V|3|W|5|O|7|2Y|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|2Z|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|30|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|31|8|@]|9|@]|A|$]]|$1|11|3|12|5|6|7|32|8|@]|9|@]|A|$]]|$1|13|3|14|5|6|7|33|8|@]|9|@]|A|$]]|$1|15|3|16|5|17|7|34|8|@]|9|@]|A|$]]|$1|18|3|-4|5|6|7|35|8|@]|9|@]|A|$]]|$1|19|3|-4|5|6|7|36|8|@]|9|@]|A|$]]|$1|1A|3|1B|5|6|7|37|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|6|7|38|8|@]|9|@$P|39|Q|3A|1|3B]|$P|3C|Q|3D|1|3E]]|A|$]]|$1|1E|3|-4|5|6|7|3F|8|@]|9|@]|A|$]]|$1|1F|3|1G|5|17|7|3G|8|@]|9|@]|A|$]]|$1|1H|3|-4|5|6|7|3H|8|@]|9|@]|A|$]]|$1|1I|3|1J|5|6|7|3I|8|@]|9|@]|A|$]]|$1|1K|3|-4|5|6|7|3J|8|@]|9|@]|A|$]]|$1|1L|3|1M|5|6|7|3K|8|@$P|3L|Q|3M|R|S]]|9|@$P|3N|Q|3O|1|3P]|$P|3Q|Q|3R|1|3S]|$P|3T|Q|3U|1|3V]]|A|$]]|$1|1N|3|1O|5|6|7|3W|8|@]|9|@]|A|$]]|$1|1P|3|-4|5|6|7|3X|8|@]|9|@]|A|$]]|$1|1Q|3|1R|5|17|7|3Y|8|@$P|3Z|Q|40|R|1S]]|9|@]|A|$]]|$1|1T|3|-4|5|6|7|41|8|@]|9|@]|A|$]]|$1|1U|3|1V|5|6|7|42|8|@]|9|@]|A|$]]|$1|1W|3|1X|5|6|7|43|8|@$P|44|Q|45|R|1S]]|9|@]|A|$]]|$1|1Y|3|1Z|5|6|7|46|8|@]|9|@]|A|$]]|$1|20|3|21|5|6|7|47|8|@$P|48|Q|49|R|1S]]|9|@]|A|$]]|$1|22|3|23|5|6|7|4A|8|@]|9|@]|A|$]]|$1|24|3|-4|5|6|7|4B|8|@]|9|@]|A|$]]|$1|25|3|26|5|6|7|4C|8|@]|9|@]|A|$]]|$1|27|3|-4|5|6|7|4D|8|@]|9|@]|A|$]]]|28|$29|$5|2A|2B|2C|A|$2D|2E]]|2F|$5|2A|2B|2C|A|$2D|2G]]|2H|$5|2A|2B|2C|A|$2D|2I]]|2J|$5|2A|2B|2C|A|$2D|2K]]|2L|$5|2A|2B|2C|A|$2D|2M]]]]

<h3>TLDR Answer</h3>
Given an email address like...
<pre><code>me@example.com
</code></pre>
The length limits are as follows:
<ul>
<li>Entire Email Address (aka: &quot;The Path&quot;): i.e., me@example.com -- <code>256</code> characters maximum.</li>
<li>Local-Part: i.e., me -- <code>64</code> character maximum.</li>
<li>Domain: i.e., example.com -- <code>254</code> characters maximum.</li>
</ul>
<h3>Source &mdash; TLDR;</h3>
The RFC standards are constantly evolving, but if you want a 2009 IETF source in a single line:
<blockquote>
...the upper limit on address lengths should normally be considered to be 256. (Source: <a href="https://www.rfc-editor.org/errata_search.php?rfc=3696&amp;eid=1690" rel="nofollow noreferrer">RFC3696</a>.)
</blockquote>
<h3>Source &mdash; The History</h3>
SMTP originally defined what a path was in <a href="https://www.rfc-editor.org/rfc/rfc821" rel="nofollow noreferrer">RFC821</a>, published August 1982, which is <a href="https://en.wikipedia.org/wiki/Internet_Standard#:%7E:text=The%20IETF%20also%20defines%20a,prior%20to%20an%20Internet%20Standard." rel="nofollow noreferrer">an official Internet Standard</a> (most RFC's are only proposals). To quote it...
<blockquote>
...a reverse-path, specifies who the mail is from.
...a forward-path, which specifies who the mail is to.
</blockquote>
<a href="https://www.rfc-editor.org/rfc/rfc2821" rel="nofollow noreferrer">RFC2821</a>, published in April 2001, is the Obsoleted Standard that defined our present maximum values for local-parts, domains, and paths. A new Draft Standard, <a href="https://www.rfc-editor.org/rfc/rfc5321" rel="nofollow noreferrer">RFC5321</a>, published in October 2008, keeps the same limits. In between these two dates, <a href="https://www.rfc-editor.org/rfc/rfc3696" rel="nofollow noreferrer">RFC3696</a> was published, on February 2004. It mistakenly cites the maximum email address limit as <code>320</code>-characters, but this document is &quot;Informational&quot; only, and states: &quot;This memo provides information for the Internet community. It does not specify an Internet standard of any kind.&quot; So, we can disregard it.
To quote RFC2821, the modern, accepted standard as confirmed in RFC5321...
<blockquote>
4.5.3.1.1. Local-part
The maximum total length of a user name or other local-part is 64
characters.
4.5.3.1.2. Domain
The maximum total length of a domain name or number is 255 characters.
4.5.3.1.3. Path
The maximum total length of a reverse-path or forward-path is 256
characters (including the punctuation and element separators).
</blockquote>
You'll notice that I indicate a domain maximum of 254 and the RFC indicates a domain maximum of 255. It's a matter of simple arithmetic. A 255-character domain, plus the &quot;@&quot; sign, is a 256-character path, which is the max path length. An empty or blank name is invalid, though, so the domain actually has a maximum of 254.

blocks|key|143752|text|可悲的是，所有其他答案都是错误的。他们中的大多数引用RFC+2821或更高版本，它甚至没有定义电子邮件地址。它所做的就是定义路径。电子邮件地址由RFC+2822+(或更高版本)定义，并且可以更长。不是有效路径的有效地址示例如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|143753|(Firstname+Lastname)+user@domain
Firstname+Lastname+<user@domain>|code-block|syntax|javascript|143754|这两个都是相同的邮箱，但写入方式不同。因此，如果您的目标是将电子邮件地址存储在数据库中，则254、256或320个八位字节的限制可能太低，尽管在实践中，这几乎不是问题。|143755|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Sadly, all the other answers are wrong. Most of them cite RFC 2821 or newer, which does not even define e-mail addresses. What it does do is define paths. E-mail addresses are defined by RFC 2822 (or newer) and can be much longer. Examples of valid addresses that are not valid paths are:
<pre><code>(Firstname Lastname) user@domain
Firstname Lastname &lt;user@domain&gt;
</code></pre>
Both of these are the same mailbox written differently. So if your goal is to store e-mail addresses in a database, a limit of 254, 256 or 320 octets might be too low, although in practise, this is rarely going to be a problem.

What is the maximum length of a valid email address? Is it defined by any standard?

What is the maximum length of a valid email address?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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有效电子邮件地址的最大长度是多少？它是由什么标准定义的吗？

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