Emails sent but not received

I've spent 3 hours this evening trying to send an email using bcc to our members. The members are in a mailing list. The email is shown as Sent but nobody receives it. I've tried splitting the members into 2 mailing groups but that didn't work. This problem is occurring randomly. Anyone have any ideas? Thanks

Hello, I am just a non-technical user of OVH cloud with e-mail. I have the same issue, but it is permanent. I can't send ANY e-mail now. The do not arrive on place. Sent but not received.

There seem to be no support. Anyone has solved this?

Thanks, Best Regards!
Greg