According to mitchell` on #pyramid, there may be an issue sending mail to BCC recipients.
I can confirm there is a problem with BCC:
Tested on my app, I'd put CC and BCC (and different variations of it)
Mails get delivered to both cc or BCC but BCC is visible in the email header and can be read.
Here's the header of email I'd received
To: marcin@****.com, marcin@*****.com
The issue here is that the code adds bcc: header into the email, that is not correct. SMTP headers are really just for email clients, thus adding bcc header makes it visible in email clients.
The fix to this issue is to remove Bcc from ADDRESS_HEADERS_WHITELIST, and
response.base['Bcc'] = self.bcc
in get_response function.
fixes #7 incorrect header (bcc) added to mail response