diff --git a/snappymail/v/0.0.0/app/libraries/snappymail/http/request/curl.php b/snappymail/v/0.0.0/app/libraries/snappymail/http/request/curl.php
index f25fef1c0..31559d112 100644
--- a/snappymail/v/0.0.0/app/libraries/snappymail/http/request/curl.php
+++ b/snappymail/v/0.0.0/app/libraries/snappymail/http/request/curl.php
@@ -47,7 +47,14 @@ class CURL extends \SnappyMail\HTTP\Request
 			\curl_setopt($c, CURLOPT_CAINFO, $this->ca_bundle);
 		}
 		if ($extra_headers) {
-			\curl_setopt($c, CURLOPT_HTTPHEADER, $extra_headers);
+			// CURLOPT_HTTPHEADER expects a flat list of "Name: value" strings.
+			// Callers may pass an associative array, in which case curl sends
+			// the bare values as malformed header lines and drops them.
+			$aHeaderLines = array();
+			foreach ($extra_headers as $mKey => $sValue) {
+				$aHeaderLines[] = \is_int($mKey) ? $sValue : "{$mKey}: {$sValue}";
+			}
+			\curl_setopt($c, CURLOPT_HTTPHEADER, $aHeaderLines);
 		}
 		if ($this->auth['user'] && $this->auth['type']) {
 			if ($this->auth['type'] & self::AUTH_BEARER ) {
diff --git a/snappymail/v/0.0.0/app/libraries/snappymail/http/request/socket.php b/snappymail/v/0.0.0/app/libraries/snappymail/http/request/socket.php
index 8b6ffc975..522bcd65a 100644
--- a/snappymail/v/0.0.0/app/libraries/snappymail/http/request/socket.php
+++ b/snappymail/v/0.0.0/app/libraries/snappymail/http/request/socket.php
@@ -43,7 +43,12 @@ class Socket extends \SnappyMail\HTTP\Request
 			$extra_headers['Authorization'] = static::$Authorization[$host];
 		}
 		if ($extra_headers) {
-			$headers = \array_merge($headers, $extra_headers);
+			// $headers is a flat list of "Name: value" strings, so an
+			// associative $extra_headers would lose its keys in the implode()
+			// below and emit bare values as malformed header lines.
+			foreach ($extra_headers as $mKey => $sValue) {
+				$headers[] = \is_int($mKey) ? $sValue : "{$mKey}: {$sValue}";
+			}
 		}
 		$headers = \implode("\r\n", $headers);
 		if (!\is_null($body)) {