We manage over 40 stores on different marketplaces like eBay, Amazon, Fnac, Priceminister, Rue du Commerce, Cdiscount etc. And we receive up to 200 emails / day. Previously we managed our email client with gmail and outlook because the others solutions we found was too expensive and no-one was compatible with ebay. So... we tried ReplyManager on last november. To be frank, The first time I saw the back office, I was afraid by the number of options and settings. But the team support is great.
So my advice is : Choose RM if you receive over 50 emails a day. At this price is simply the best solution on the market.
François-Xavier Morre CEO of Sonuts.com / Father, hardworker and Marketplace Addict