We have a problem that PHPList is not sending all emails, but only most of them. Of 1,603 recipients in this list 18 where not sent with the log “Could not instantiate mail function”. Then the system tried to send each address around 5,000 times.
All other 1,585 emails were sent. I use PHPMAILER = 1, and the limit is set to 235 email every 240 seconds (equals 3,525 emails per hour, our provider 1&1 has a limit of 5,000 emails per hour).
I would be happy for any hints about this issue. It is also filling up my database…