<p>Every <strong>valid email</strong> consists of a <strong>local name</strong> and a <strong>domain name</strong>, separated by the <code>'@'</code> sign. Besides lowercase letters, the email may contain one or more <code>'.'</code> or <code>'+'</code>.</p>
<ul>
<li>For example, in <code>"alice@leetcode.com"</code>, <code>"alice"</code> is the <strong>local name</strong>, and <code>"leetcode.com"</code> is the <strong>domain name</strong>.</li>
</ul>
<p>If you add periods <code>'.'</code> between some characters in the <strong>local name</strong> part of an email address, mail sent there will be forwarded to the same address without dots in the local name. Note that this rule <strong>does not apply</strong> to <strong>domain names</strong>.</p>
<ul>
<li>For example, <code>"alice.z@leetcode.com"</code> and <code>"alicez@leetcode.com"</code> forward to the same email address.</li>
</ul>
<p>If you add a plus <code>'+'</code> in the <strong>local name</strong>, everything after the first plus sign <strong>will be ignored</strong>. This allows certain emails to be filtered. Note that this rule <strong>does not apply</strong> to <strong>domain names</strong>.</p>
<ul>
<li>For example, <code>"m.y+name@email.com"</code> will be forwarded to <code>"my@email.com"</code>.</li>
</ul>
<p>It is possible to use both of these rules at the same time.</p>
<p>Given an array of strings <code>emails</code> where we send one email to each <code>emails[i]</code>, return <em>the number of different addresses that actually receive mails</em>.</p>
