SERVER -&gt; CLIENT: 220-cpanel05wh.bkk1.cloud.z.com ESMTP Exim 4.96.2 #2 Mon, 12 Jan 2026 06:55:35 +0700 220-We do not authorize the use of this system to transport unsolicited, 220 and/or bulk e-mail.<br>
CLIENT -&gt; SERVER: EHLO thanakiat.com.67332121-34-20190102105002.webstarterz.com<br>
SERVER -&gt; CLIENT: 250-cpanel05wh.bkk1.cloud.z.com Hello thanakiat.com.67332121-34-20190102105002.webstarterz.com [163.44.198.45]250-SIZE 52428800250-8BITMIME250-PIPELINING250-PIPECONNECT250-AUTH PLAIN LOGIN250-STARTTLS250 HELP<br>
CLIENT -&gt; SERVER: STARTTLS<br>
SERVER -&gt; CLIENT: 220 TLS go ahead<br>
SMTP Error: Could not connect to SMTP host.<br>
CLIENT -&gt; SERVER: QUIT<br>
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SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting<br>