Why would mail campaign fail to deliver to valid email address?

[Bev]

An emailed newsletter failed to reach a recipient, who knew about it because the dreaded mailer-daemon sent a notice to said address to let him know it couldn't deliver. Since that someone is my boss, I'm now supposed to explain why.

I know the address itself is valid. Could there be something I should be doing in the settings or newsletter itself that will keep it from being rejected by my boss's personal mailbox?

[Moved from Forum Lounge to product-specific workspace - Mod]

[ChantalR · Accepted solution]

I would start by investigating the mailer-daemon notice that was sent. Did it not give a reason for why it couldn't deliver the email? There may be information provided in the notice that might indicate why the email wasn't delivered.