Incorrect format in Bcc

I have set-up a new distribution list using addresses I have used for a long time, when I try to send to this group using Bcc, a pop-up window says ‘recipients have an incorrect format’ clicking ‘send anyway’ does not work either. I cannot see that the addresses have changed in any way and can send to individuals within that group. 165 addresses. Thanks

Hi, what version of eM Client are you currently using on your computer, can you please check for the exact version number in Help > About? What mail service vendor are you using with eM Client? Are you using a POP or an IMAP account?

Can you please make a screenshot of the error that you’re seeing and a screenshot of the distribution list’s details?

Thank you,