First of all, I'd like to thanks for such a great plugin :-)
I'm having an issue hard to track down, I have about 1500 subscribers distributed in 8 lists. One of those lists have 10 addresses used for test purpose.
In every campaign I send, I'm receiving in about 3 (of those 10 addresses) a blank email with just the tracking img.
Is there any setting or configuration that I should be concerned?
I'm in a shared hosting, sending 10 mails every 5 minutes (in batch mode)
I'll apreciate any help.