Sadly, email is not perfectly reliable, thanks to spam filters, addressing errors, and server failures. With certain types of email, it’s worth double-checking that a message reached its destination.
One example of that we see when supporting our clients is with questions about phishing email (which criminals use to try to trick you into revealing passwords, credit card info, or other sensitive information). Phishing messages can be tricky to identify — that’s their goal. If you’re forwarding a possible phishing email to us or another trusted technical contact for evaluation, remember that spam filters often catch such messages, so your question may go unseen.
To work around this awkwardness, send a separate message saying you’ve forwarded something that might be a phishing message. That way the recipient knows to check their Junk mailbox if need be. It’s helpful if you can include the Subject line of the suspect message, or even a screenshot of the message itself.