开云体育

One possibility is the "Gmail effect". Gmail tends to hide the message that returned from the group because the original (as sent) copy it is already in the conversation. Even with conversation mode turned off. If his email service is Gmail (or a rebranding of the Gmail interface) he'll likely find the returned messages tucked into the Sent folder instead of his Inbox. He can spot this case by posting from your group's web interface; if he receives those but not the messages posted from his email interface then there's a work-around for this in Groups.io: have him check the I always want copies of my own emails box on the Preferences page of his account.

Another possibility relates to email services that interpret a message from the outside (ie, delivered to them by Groups.io) which claims to be from their user as fraudulent. Most often those are delivered to Spam, but some services have been known to reject them outright. You can spot this case by looking at the Email Delivery History tab of his page in your group's Members list. You may find messages from him in his list of Recent Bounces.

Shal