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Some advice needed

Hello all,
We have just launched our first mobile game for Android ParaBall: Ball Balance, and we have started getting e-mails from all kind of services such as appEnhancer (some sort of review exchange service) and from some publishers such as (lootboy-asking a fraction of our earnings in order for them to promote our game).
What is your opinion/experience with this type of solicitor? Are they legit? Should we consider such offers at the beginning of the road?
If you would like to check out our game here it is: https://play.google.com/store/apps/details
Thanks & looking forward to your feedback