Returned mail I never sent

Returned mail I never sent

I have a few email accounts at one domain and on only one of these accounts I have been getting what appears to be returned mail. I've never sent the emails in question. They appear to be sent from a legitimate address to addresses that do not exist on my email setup. I'm not sure if this is just spoofing or if the account has been compromised. We use very secure passwords and this particular account is accessed via IMAP on three computers in the same physical location only.

Here are the headers:

Delivered-To: accounting@morrispaint.com
Received: from mail.zoho.com by mx.zohomail.com
    with SMTP id 1473875069587524.7413932438247; Wed, 14 Sep 2016 10:44:29 -0700 (PDT)
Date: Wed, 14 Sep 2016 10:44:29 -0700
From: mailer-daemon@mail.zoho.com
To: accounting@morrispaint.com
Message-Id: < 15729ccca66.f493596e1379973290.-1017368165318518904@zohomail.com>
Subject: Undelivered Mail Returned to Sender
MIME-Version: 1.0
Content-Type: multipart/mixed;
    boundary="----=_Part_39188_428399705.1473875069542"
User-Agent: Zoho Mail
X-Mailer: Zoho Mail
X-ZohoMail: Z_306405428 SPT_1 Z_306372661 SPT_1 Si CHF_MF_NL SS_10 UW48 UB48 COSF2D FMWL UW48 UB48 SGR3_1_2_0_27046_535
X-Zoho-Virus-Status: 2