In many cases in order to insure proper mail delivery special records need to be created on Broker-side Domain (DNS Record).
In most cases the SPF record is enough to ensure mail deliverability.
SPF record is a TXT record. and the following is all that may be needed from the Trader's Room Side:
v=spf1 include:amazonses.com ~all
Howver it is likely that you may want to incliude the SPF record of your email provider so that your email would also be deliverable.
This example is an SPF record for Trader's Room and for Google Apps for Business:
v=spf1 include:amazonses.com include:_spf.google.com ~all