from looks of your domain dns you only have two Google apps mx records listed  you should have  4  google apps mx records and you don't have a spf either  SPF  information here http://support.google.com/a/bin/answer.py?hl=en&answer=178723

1	ASPMX.L.GOOGLE.COM
5	ALT1.ASPMX.L.GOOGLE.COM
5	ALT2.ASPMX.L.GOOGLE.COM
10	ASPMX2.GOOGLEMAIL.COM
10	ASPMX3.GOOGLEMAIL.COM