I have a problem with announcement which it sends 8,9 mails to an email but 0 to some others.
I have 4 users registered with email@example.com, second@gmail,third@gmail,firstname.lastname@example.org relatively.
I made an announcement yesterday. After 8,9 hours, email@example.com and firstname.lastname@example.org received 8,9 same email. But third@gmail,email@example.com haven’t received any mails yet.
I set 60 minutes and 100 mails in setting
Are you using any SMTP plugin or any other plugin which change wp_mail function? Your issue seems return false from wp_mail function all the time and it should not be. I will try to add a filter to bypass this check next version.