In most distributors, you'll have no control or info of which images go to each partner. There are partners you've never heard of; maybe some day you'll learn their name when there is a sale. 

Regarding Robert Harding, there is something strange in what you say. My camera is 21Mp and I have no problem in having them accepted in Robert Harding because of size (unless you crop significantly!).

If you're heading the distributor way, you must relax and take it easy. You can't control each image and it sure takes time to see images being distributed to partners and to start receiving information about sales.

Needs updating but here's a list:

https://brutallyhonestmicrostock.com/2017/07/05/alphabetical-list-of-midstock-agencies/

RH has a 50mb uncompressed requirement. I believe that's 14mb compressed.

That's a great list Alex, thanks!
Any information about sales?

https://brutallyhonestmicrostock.com/2019/03/01/first-ever-earnings-report-feb-2019/

Now where's my swiss chocolate!?

Great, thank you

Haha, well, when (or if ) our earnings will hit the bottom finally as everyone predicts (since inception), I'll turn my studio into a Chocolaterie and will let you know first!

I find Robert Harding very confusing, do they accept non-exclusive content? They seem to have lots of non exclusive content on their website, but only accept contributor with exclusive images?

They are image-exclusive - RM/RF.

Ah ok thanks, the non-exclusive content they have must be from somewhere else. Looking at the numbers they have 94700 images but only 2015 when filtered on exclusive.   

Ah yes, I should explain better.

They have an initial 5/6-month period when images are exclusive to RH before they distribute. They label the images exclusive with a star.