Web design - Fixing length of To, CC and BCC text fields

I am designing a web page to accept email addresses to be used for user notification. In the process trying fix the length of to, cc and bcc fields.

As per RFC 2821/3696 max length of an email address can go up to 256 characters, and maximum number of email addresses an email exchange can be up to 125. That says the max length of the field coming around (256*125) ~ 35000 characters.

Providing such a text box is practically not convincing/viable.

Would like to know if there are any standards/best practices to fix number of characters to, cc, bcc field should allow.