Spark/Xtra email

[king1]

are these just replies to customer enquiry emails or are we talking mailing list mail outs etc

Replies to any emails including to enquiring customers. We use ReadNotify and see from that quite a few emails just go unopened. I will often follow up with a resend forwarded using my Gmail account which usually gets a response.

For mailouts we use Mail Chimp and the amount of non-receipts would seem to indicate the spamming problem happens there too.

it's an interesting problem, I think you have to start from a perspective that spam is prevalent and many people consider legitimate mailing lists that they sign up to as spam/junk when they no longer want it, rather than unsubscribing.  some folks don't discern the difference from legitimate spam, so I think you could assume that some folks have used the mark as spam option...

The other point is I don't think you could consider the few emails that go unopened as actually being unopened.  Many email client programs (thunderbird,Outlook etc) block external server connections in an email message until such time as the user accepts external sources (like images and scripts)   

I'm pretty sure (recipients using... ) providers like gmail and outlook (web based), will preload the mail for their email users (prior to the user checking email) so these ones are probably ok...  

there is also a note on the readnotify faq that for invisible sending option "Sending emails this way may decrease reliability."

Not sure about using the "office 365 for redirection" kind of doesn't make much sense, did they mean that you should shift your email over to 365 perhaps?