虽然不可能使用HTML来格式化你的电子邮件正文，你可以添加换行符，就像之前建议的那样。

如果你能够使用javascript，那么“encodeURIComponent()”可能会像下面这样使用…

var formattedBody = "FirstLine \n Second Line \n Third Line";
var mailToLink = "mailto:x@y.com?body=" + encodeURIComponent(formattedBody);
window.location.href = mailToLink;

Whilst it may not be possible within the parameter of the URL, there is a cheeky solution which allows full HTML. The concept is that you have a hidden element on the page (I am using Bootstrap and Jquery in the example below) which is temporarily revealed and the HTML copied (as per here: How to copy text from a div to clipboard). Following that, you redirect the user to the Mail link so in effect all they then have to do is hit Paste within their designated mail program. I've only tested this on Linux/Thunderbird but the paste also works into Gmail web.

<div id="copyEmailText" class="d-none"><p><strong>This is some HTML</strong>. Please hit paste when your email program opens.</p>

function copyDivToClipboard(element) {
    var range = document.createRange();
    range.selectNode(element);
    window.getSelection().removeAllRanges(); // clear current selection
    window.getSelection().addRange(range); // to select text
    document.execCommand('copy');
    window.getSelection().removeAllRanges();// to deselect
}

$('#copyEmail').on('click',function(){
    $('#copyEmailText').toggleClass('d-none');
    copyDivToClipboard($('#copyEmailText')[0]);
    window.location.href = 'mailto:?subject=Email subject text';
    $('#copyEmailText').toggleClass('d-none');
})

任何人都可以尝试以下(mailto函数只接受明文，但在这里我展示如何使用HTML内文属性，以及如何添加锚作为mailto主体参数):

//Create as many html elements you need.

const titleElement = document.createElement("DIV");
titleElement.innerHTML = this.shareInformation.title; // Just some string

//Here I create an <a> so I can use href property
const titleLinkElement = document.createElement("a");
titleLinkElement.href = this.shareInformation.link; // This is a url

...

let mail = document.createElement("a");

// Using es6 template literals add the html innerText property and anchor element created to mailto body parameter
mail.href = 
  `mailto:?subject=${titleElement.innerText}&body=${titleLinkElement}%0D%0A${abstractElement.innerText}`;
mail.click();

// Notice how I use ${titleLinkElement} that is an anchor element, so mailto uses its href and renders the url I needed

It is worth pointing out that on Safari on the iPhone, at least, inserting basic HTML tags such as <b>, <i>, and <img> (which ideally you shouldn't use in other circumstances anymore anyway, preferring CSS) into the body parameter in the mailto: does appear to work - they are honored within the email client. I haven't done exhaustive testing to see if this is supported by other mobile or desktop browser/email client combos. It's also dubious whether this is really standards-compliant. Might be useful if you are building for that platform, though.

正如其他响应所指出的，在将encodeURIComponent嵌入到mailto:链接之前，还应该在整个正文上使用encodeURIComponent。

虽然不可能使用HTML来格式化你的电子邮件正文，你可以添加换行符，就像之前建议的那样。

如果你能够使用javascript，那么“encodeURIComponent()”可能会像下面这样使用…

var formattedBody = "FirstLine \n Second Line \n Third Line";
var mailToLink = "mailto:x@y.com?body=" + encodeURIComponent(formattedBody);
window.location.href = mailToLink;

我已经使用了这个，它似乎与outlook工作，不使用html，但你可以格式化文本与换行符，至少当正文被添加为输出。

<a href="mailto:email@address.com?subject=Hello world&body=Line one%0DLine two">Email me</a>