[AccessD] A2003:Size of an Email String

Hello all
I am building a string of email addresses to include in the BCC field of
an outlook email message

I have discovered if I have about 400 recipients then the email ends up
in my drafts folder ready to go
With a big long BCC string - So far so good - The string length of all
the emails is about 6000 characters ~+or-
When there is approx 400 Email addresses

But as soon as I get above that (Say 500 or even 1,100 email addresses)
the email does not appear in the drafts folder
The string length with 1100 email addresses is about 24,000 characters
~+or-

I am thinking there is some limit to the number of characters in
Outlook's BCC field 
Does anyone know about this?
Or can anyone point me in the direction of an answer?

Many thanks

Darren