I read the RFC 822 very carefully but I was not able to read something about
a limitation in the BCC Field. Is there such a thing as a maximum number of
characters that can be written in the BCC field?
no. and since Bcc processing is done by the submitter's user agent
(or in some cases the submitter's MTA acting on behalf of the user agent),
length of Bcc fields matters even less than length of other fields.
Is there a maximum limit of characters for email at all?
no. there is a suggested maximum length per line (between CRLF pairs),
but header fields can occupy more than one line. SMTP servers can
place a restriction on the size of incoming messages, but there are
no inherent length restrictions on header fields or body parts.
Keith