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:
The rejected e-mail address was 'firstname.lastname@example.org'. Subject 'Max Rcpt Test 2', Account: 'mail.yourdomain.com', Server: 'mail.yourdomain.com', Protocol: SMTP, Server Response: '555 syntax error (#5.5.4)', Port: 25, Secure(SSL): No, Server Error: 555, Error Number: 0x800CCC79
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.
Article ID: 50
Last updated: 28 Jul, 2018