Some email systems verify the sending email address, against IP address. With these systems, email which originates from a Blogger account that's based on a non GMail email address, and comes from a Blogger / Google IP address, is going to present a problem, to the account owners.
If your Blogger account is based on a non GMail email address - and your blog provides any of various "notification" / "subscription" services.
- "BlogSend" (aka "Email posts to") based subscriptions.
- Comment moderation or notification email.
- Your readers like to comment authenticated, and select the "Email follow-up comments ..." option.
- The Blogger supplied "Contact Me" accessory gadget.
Note that "bounced" email may not be treated as spam. Some "bounced" email never gets as far as a spam filter - it may simply be rejected. You will look, in vain, in "Bulk", "Inbox", and "Spam" folders.
Blogger originated email, to certain email clients, will be bounced, because Blogger sends the notification / subscription email with your Blogger account (your readers account) mentioned, as the sender.
With Blogger comment moderation / notification email coming from a non GMail based Blogger account, and sent from a Google IP address, an email client such as AOL, HotMail, or Yahoo, which verifies email address against IP address, is going to reject the incoming email message. This is because "Sender Policy Framework", which AOL, HotMail, Yahoo, and other email systems use, detects the originating address as "spoofed".
Spoofing is a common technique used by spammers, in hiding their email identity. Most email based spam is spoofed - so email systems, which use DKIM or SPF filters to identify spam, will bounce any messages which do not verify properly - when IP address and originating email address are compared.
The problem may also involve comment subscription email. This may result in bounce messages being sent to the person attempting to publish a comment. This causes more confusion.
The solution, to the problem with moderation / notification email, is simple - but unlikely to satisfy many Blogger account owners. You will have to use a GMail email address, for comment moderation or notification. Until Blogger Engineering figure a better way to send the moderation / notification email, email clients such as AOL, HotMail, and Yahoo will have this problem.
If the blog owner changes ownership of a blog, from a non GMail based Blogger account to a GMail based account, and neglects to change the comment moderation / notification email address, the bounce messages will likely continue. What might happen with comment subscription email is yet to be determined.
This problem, as discussed above, affects the comment moderation process. While annoying to some blog owners (as noted, those using non GMail based Blogger accounts / email addresses), the problem is not all that severe. Affected blog owners can use the Blogger dashboard Comments wizard, to moderate comments. Also, blog owners, who moderate comments after they are published, may not even notice this problem.
This problem may also affect membership invitations to private / team blogs This will be a more severe issue, in that this problem will affect all blogs with owners using non GMail email addresses, and with prospective blog members on large non GMail email systems - because there will be no dashboard based wizard - and no possibility of moderation after publishing.
The involvement of Google Apps based (non "gmail.com" Google email) Blogger accounts, and Blogger originated email, is yet to be studied. Also please note that Blogger account email addresses, and comment moderation / notification email addresses, do not have to be the same - and this may cause still more confusion.