not receiving emails from clients that have icloud emails

For a while now that clients using emails [...@i](mailto:[email protected])cloud.com are telling me that they sent me emails, but the fact is that I never get them and apparently they don´t receive any bounce back notice.

What can I do to fix this?

update: this has happened with more than one iclound account, thus why i´m a bit concerned that the problem might be on my side.