Mac mail error: "4.5.3 Too many recipients"

[spozgay]

I am trying to send an email to 26 recipients. I tried individually inserting their email addresses separately and received the "too many recipients" error. Then I tried making those same recipients a group in Address Book and resending - I got the same error message. Immediately above the error message (every time I try sending the email, the "Message delivery failed" window states that 4 of the recipients were not found - but I sent emails to all 4 of these people within the last 3-5 days and I am certain their email addresses are correct.

Can anyone help me??!!