Thuderbird Email With Bcc

Just started checking out Thuderbird and imported a large list into it. Normally send these bulk in Bcc so they cant see each others emails. Opened the list in contacts and selected all and send mail although when the window opened they were all on a separate line with CC preselected. Seems the only way to change this was to do it one at a time which with a large list would be to time consuming. Is there any other way to send a large list in this app as Bcc or so that its the default send or a way to change them all at once.

Also does anyone know an email client that can take a large list and send them individually. That way each recipient would get the email addressed to them only without the need for CC or BCC fields. Only way Ive figured to do that is with a macro it seems. The macro works fine although takes allot of time to complete...

Start a new email.
Put yourself as the first recipient.
Select bcc in the second recipient then enter the list name, not the individual members. Just one bcc line for the whole list.
Complete your mail and send it.

Says the email is not valid since it not in the forum of an email with @ and it must be corrected prior to sending...

This is all I did.

When I try to to do this I get an error when I click send as you can see in the screenshot below. However I did find that if I press Contacts above I can the select the list in the dropdown and highlight all the names and then right click and choose send Bcc which works similar as Outlook does...

Strange.

I thought that it was possibly because there's no primary recipient - I sent it to myself when I tried this - but I've just tried again with just a mail list in the Bcc line and don't get any problems.

When you select the list do you you type it in manually or select it somehow...