We keep having this small issue come up and manually fixing it. It might be others may have or soon might have a similar problem.
The core issue is some ISP's block generated mail messages if the "From" address is not within their domain. I suppose we can thank spammers for this.
Generally mail leaving Word Press very nicely uses the administrator email adddress as the "From" address and everything works nicely.
However, there is at least one place when someone makes a comment on an item, after it gets approved, Word Press sends a message to the originator of the item showing it coming from the creator of the comment.
Of couse the "creator of the comment" is generally the email address of the person who made the comment and is going to be off in some other domain which immediately gets blocked .
So we locate these and manually re-code to make the "From" address be the admin login and add a "Reply-to:" in the header to allow an easy reply to the commentor.
To make it easy....could you please fix this in some future release to spare us this pain (finding the location in the code takes some time).
Our suggestion would be ...
1) Use the RFC822 field "Sender" to always to be the Administrator email address as configured. (Currently Word Press does not set this.)
2) Set the RFC822 field "Reply-to" to what is the "from" field
3) Set the RFC822 field "From" the way you do right now.
I suppose if you want to do just the minimum you could add "Sender" as the administrator email to all messages and call it a day.
This would greatly easy our workload when we configure Word Press.
It would perhaps be more elegant addressing in since the "administrator" on the server is really the one generating the message even though you might be doing it on "behalf" of the person creating the item.
Let us know what you think.
Thanks for the consideration.