That's most likely the reason: OVH is well known for their lack of attention on spammers using their VPSs, so most operators will just filter their IP blocks.

That's most likely the reason: OVH is well known for their lack of attention on spammers using their VPSs, so most operators will just filter their IP blocks. I run a low volume email server and 100% of the connections from OVH blocks are spam/phishing/vuln-scanning/etc. It's true that Gmail could do more to help low volume operators understand deliverability problems, but in my opinion OVH should be doing something about their spam issue. My advice when looking for a VPS provider for running an email server is to read their AUP and check their blocks on Talos.