I'm very new to the world of mail servers and have been following all the information I can find to get one set up on an Ubuntu 14.04 x86_64 vm with Mail-in-a-box. Everything works, but mail-tester.com indicates my DKIM record is invalid. Here's what my zone file looks like:

$ORIGIN zetamacs.com.
$TTL 1800
zetamacs.com. IN SOA ns1.digitalocean.com. hostmaster.zetamacs.com. 1456938287 10800 3600 604800 1800
zetamacs.com. 1800 IN NS ns1.box.zetamacs.com.
zetamacs.com. 1800 IN A 159.203.243.150
www.zetamacs.com. 1800 IN CNAME zetamacs.com.
zetamacs.com. 1800 IN MX 10 box.zetamacs.com.
ns1.box.zetamacs.com. 1800 IN A 173.245.58.51
ns2.box.zetamacs.com. 1800 IN A 173.245.59.41
box.zetamacs.com. 1800 IN A 159.203.243.150
zetamacs.com. 1800 IN NS ns2.box.zetamacs.com.
zetamacs.com. 1800 IN MX 10 zetamacs.com.
mail.domainkey.zetamacs.com. 1800 IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDQ7KPVFTRqniC7k/jQlE+J2qxEjb1IjxqUBxm/Fi9c02GEx9JI62uPsjJCzE5GX+cLQr5UfbpE2Qn1IKbNGacAs2txoSSK30sVzYp4mBFbUUm0pLBdkNZAqBeUzP4Wdxpzql/KIEDh3akTmkgrgiP68jVShQjzWlkRcs7oqXAmZwIDAQAB"
zetamacs.com. 1800 IN TXT "v=spf1 include:spf.google.com ip4:159.203.243.150 ~all"
ns3.box.zetamacs.com. 1800 IN A 198.41.222.173
zetamacs.com. 1800 IN NS ns3.box.zetamacs.com.
_dmarc.zetamacs.com. 1800 IN TXT "v=DMARC1; p=quarantine; rua=mailto:james@zetamacs.com; ruf=mailto:james@zetamacs.com; fo=0:1:d:s; aspf=s"

(Sorry that it's such a disorganized mess)

Is there a syntax error in here I haven't seen? Any help would be appreciated!