I have exactly the same problem as described.
Hi,
as per your recommendation, I have limited BCC to 10 emails and it looks like the issues solved.
Thanks,
Simonas
I have tryed to set BCC to 100 and notify 23 registered users, but it failed. Talked with hosting provider… they also do not have any limitation. Only 100 email per hour. But thats OK with me.
Simonas