Verify DNS SRV Records for Office 365

Check on linux:

# host -t SRV _sipfederationtls._tcp.yourdomain.com
_sipfederationtls._tcp.yourdomain.com has SRV record 100 1 5061 sipfed.online.lync.com.

Check on a windows system:

c:\> nslookup
> set type=any
> set verbose
> _sipfederationtls._tcp.yourdomain.com
_sipfederationtls._tcp.yourdomain.com      SRV service location:
          priority       = 100
          weight         = 1
          port           = 5061
          svr hostname   = sipfed.online.lync.com