diff --git a/lib/IMAP/ImapMessageFetcher.php b/lib/IMAP/ImapMessageFetcher.php
index 4d38dd2f79..0d476329e8 100644
--- a/lib/IMAP/ImapMessageFetcher.php
+++ b/lib/IMAP/ImapMessageFetcher.php
@@ -314,8 +314,11 @@ private function getPart(Horde_Mime_Part $p, string $partNo, bool $isFetched): v
 			}
 		}
 
+		$isAttachment = ($p->isAttachment() || $p->getType() === 'message/rfc822') &&
+			!in_array($p->getType(), ['application/pgp-signature', 'application/pkcs7-signature', 'application/x-pkcs7-signature']);
+
 		// Regular attachments
-		if ($p->isAttachment() || $p->getType() === 'message/rfc822') {
+		if ($isAttachment) {
 			$this->attachments[] = [
 				'id' => $p->getMimeId(),
 				'messageId' => $this->uid,