SRV record "(out of zone) is a CNAME (illegal)"

[enigmedia]

Hi All: I'm trying to set up a SRV record for a zone, and when I run checkzone I
see the following error:

[root at default root]# named-checkzone -w /var/named mydomain.com db.mydomain.com
db.mydomain.com:13: TTL set to prior TTL (3600)
zone mydomain.com/IN: _sipfederationtls._tcp.mydomain.com/SRV
'sipfed.online.lync.com' (out of zone) is a CNAME (illegal)

My SRV record is:

_sip._tls       SRV 100 1 443   sipdir.online.lync.com.

Is there something wrong with my SRV record, or is this just a warning about
pointing to a different domain?