Issues with Mailster

Hi,

I am using Offload SES which is working perfectly fine. I have pasted my AWS keys in the wp-config.php file.

The problem rises when I install another newsletter plugin Mailster to use it with gravity forms. It recommends using AWS. Now when I enter the same keys there my site stops working and restarts working when I change from AWS to WordPress mail for Mailster.

Any help will be highly appreciated.