TOPIC: confirmation mail sometimes not sent to BCC

In the backend settingss I have the BCC mail option activated but today I realized that not every booking ist sent to this adress. Whenever I edit a booking in the backend this confirmation is sent to this BCC mail adress.
Strange behaviour...

Only to the BCC email?

When BCC email is active there are three mails send (Default settings) -> whenever a booking is done (does not matter where).

-> participant email
-> organizer email
-> bcc email

And that together. Maybe the ISP / provider is blocking this? Because 3 emails are sent directly (same time) after another.

Yves

but if the provider would denie that action every mail had to be blocked.. It's only sometimes that I don't get the BCC mail. Have not yet an idea what settings cause that problem