diff --git a/lib/IMAP/ImapMessageFetcher.php b/lib/IMAP/ImapMessageFetcher.php
index 4d38dd2f79..ef3e7ed699 100644
--- a/lib/IMAP/ImapMessageFetcher.php
+++ b/lib/IMAP/ImapMessageFetcher.php
@@ -459,7 +459,6 @@ private function loadBodyData(Horde_Mime_Part $p, string $partNo, bool $isFetche
 			}
 
 			$data = $fetch->getBodyPart($partNo);
-
 			$p->setContents($data);
 		}
 
@@ -470,11 +469,30 @@ private function loadBodyData(Horde_Mime_Part $p, string $partNo, bool $isFetche
 
 		// Only convert encoding if it is explicitly specified in the header because text/calendar
 		// data is utf-8 by default.
-		$charset = $p->getContentTypeParameter('charset');
-		if ($charset !== null && strtoupper($charset) !== 'UTF-8') {
-			$data = mb_convert_encoding($data, 'UTF-8', $charset);
+		$charset = mb_detect_encoding($data, 'UTF-8', true);
+		if (!$charset) {
+			$charset = $p->getCharset();
+		}
+
+		// Try the email encoding first
+		$converted = @mb_convert_encoding($data, 'UTF-8', $p->getCharset());
+		if ($converted) {
+			return $converted;
+		}
+
+		// Fallback
+		$charset = mb_detect_encoding($data, null, true);
+		$converted = @mb_convert_encoding($data, 'UTF-8', $charset);
+		if ($converted) {
+			return $converted;
+		}
+
+		// Might be a charset that PHP mb doesn't know how to handle, fall back to iconv
+		$converted = iconv($charset, 'UTF-8', $data);
+		if ($converted === false) {
+			throw new ServiceException('Could not detect message charset');
 		}
-		return (string)$data;
+		return $converted;
 	}
 
 	private function hasAttachments(Horde_Mime_Part $part): bool {