Messages which receive the "Approved" action in Symantec Messaging Gateway (SMG) content quarantine or released from the Suspect Virus Quarantine may have two identical DKIM-Signature headers added to the message.
Example
DKIM-Signature: v=1; a=rsa-sha256; d=domain.com; s=us; c=relaxed/simple; q=dns/txt; [email protected]; t=1521020644; x=1523612644; h=From:Subject; bh=oASaH+O1iRyzV46XL+gDL1HlZ6oQgKY1TR5j2rU++b0=; b=CjoH4gktbtOm8DGRTX98wlmg/XV7ZVTk+zjaeeKyYzdOUbMV3qOI5OLlPqCLSIf8 uQaRhpsMT+/4d4iqr+UVTk0WZkKn5UftJCgl+YKRBHHIE0ewEQcQIy1qPU9KgZHl OBl7MKm/BOD5wqaid+jTYPjS3JzGlgcfx29lUc4jIIg=; DKIM-Signature: v=1; a=rsa-sha256; d=domain.com; s=us; c=relaxed/simple; q=dns/txt; [email protected]; t=1521020644; x=1523612644; h=From:Subject; bh=oASaH+O1iRyzV46XL+gDL1HlZ6oQgKY1TR5j2rU++b0=; b=CjoH4gktbtOm8DGRTX98wlmg/XV7ZVTk+zjaeeKyYzdOUbMV3qOI5OLlPqCLSIf8 uQaRhpsMT+/4d4iqr+UVTk0WZkKn5UftJCgl+YKRBHHIE0ewEQcQIy1qPU9KgZHl OBl7MKm/BOD5wqaid+jTYPjS3JzGlgcfx29lUc4jIIg=;
Messages are being signed both before delivery to the quarantine and after quarantine release.
This is a known issue and will be addressed with a future release.
The addition of a second DKIM-Signature header does not affect message delivery or DKIM authentication.