Diadem Mail servers have implemented a check on the number of recipients that one enters in the "To"/"CC"/"Bcc" field in the e-mail to be sent. The Max number of recipients that you can send a mail to at a time has been restricted to 25. If you get the below mentioned errors then you can be sure that you have exceeded the Maximum number of recipients allowed in our server".
Error encountered from Webmail service:
There was an error sending your message: sendmail returned error code 100
Error encountered from Outlook/Outlook express:
Error encountered from VPOP3 server:
"555 Syntax error (# 5.5.4) "
The mail that you try to send with number of recipients exceeding the mentioned limit of 25 would be rejected.