From e588719eec972f8b76fe6b3c38e50e60236aa5a0 Mon Sep 17 00:00:00 2001
From: Arnt Gulbrandsen <arnt@gulbrandsen.priv.no>
Date: Wed, 23 Oct 2024 15:36:34 +0200
Subject: [PATCH] Send unencoded UTF8 in subject/body text when SMTPUTF8 allows
 that.

---
 src/PHPMailer.php                |  9 ++++++++-
 test/PHPMailer/PHPMailerTest.php | 11 +++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/PHPMailer.php b/src/PHPMailer.php
index 5417d507..2e74a70c 100644
--- a/src/PHPMailer.php
+++ b/src/PHPMailer.php
@@ -2926,7 +2926,9 @@ class PHPMailer
         $bodyEncoding = $this->Encoding;
         $bodyCharSet = $this->CharSet;
         //Can we do a 7-bit downgrade?
-        if (static::ENCODING_8BIT === $bodyEncoding && !$this->has8bitChars($this->Body)) {
+        if ($this->UseSMTPUTF8) {
+            $bodyEncoding = static::ENCODING_8BIT;
+        } else if (static::ENCODING_8BIT === $bodyEncoding && !$this->has8bitChars($this->Body)) {
             $bodyEncoding = static::ENCODING_7BIT;
             //All ISO 8859, Windows codepage and UTF-8 charsets are ascii compatible up to 7-bit
             $bodyCharSet = static::CHARSET_ASCII;
@@ -3572,6 +3574,11 @@ class PHPMailer
      */
     public function encodeHeader($str, $position = 'text')
     {
+        $position = strtolower($position);
+        if($this->UseSMTPUTF8 && !("comment" === $position)) {
+           return trim(static::normalizeBreaks($str));
+        }
+
         $matchcount = 0;
         switch (strtolower($position)) {
             case 'phrase':
diff --git a/test/PHPMailer/PHPMailerTest.php b/test/PHPMailer/PHPMailerTest.php
index 15693a0a..87e5888b 100644
--- a/test/PHPMailer/PHPMailerTest.php
+++ b/test/PHPMailer/PHPMailerTest.php
@@ -1254,6 +1254,17 @@ EOT;
         $this->Mail->addAddress('spın̈altap@spın̈altap.invalid', '');
         $this->Mail->preSend();
         self::assertStringContainsString("spın̈altap@spın̈altap.invalid", $this->Mail->createHeader());
+
+        //Sending unencoded UTF8 is legal when SMTPUTF8 is used,
+        //except that body parts have to be encoded if they
+        //accidentally contain any lines that match the MIME boundary
+        //lines. It also looks good, so let's do it.
+
+        $this->Mail->Subject = 'Spın̈al Tap';
+        self::assertStringContainsString("Spın̈al", $this->Mail->createHeader());
+        $this->Mail->Body = 'Spın̈al Tap';
+        $this->Mail->preSend();
+        self::assertStringContainsString("Spın̈al", $this->Mail->createBody());
     }
 
     /**