This will be very hard to diagnose as I don't get it with any mail server so far.sander wrote: 91 10.302784 195.241.79.132 192.168.178.32 SMTP S: 554 SMTP synchronization error
This doesn't happen when you have just one recipient?
Does it happen in the first or the last email?
What if there are three?
OSX makes no difference, I'll test it explicitly, but I'm quite sure.rembo10 wrote: I'm on OS X if it makes a difference.
is using the whole email address field as the $to variable within the email
The $to variable is correct, it holds just one address.
Easy to check if you would use it again in the email body.