Some ISPs might not return an error message when they detect outgoing messages as unsolicited commercial email. In these cases, your message might appear to be sent normally — it leaves your Outlook Outbox and appears in your Sent Items — but it's never actually delivered to the recipient.

TPM 2.0 is used in Windows 11 for a number of features, including Windows Hello for identity protection and BitLocker for data protection. In some cases, PCs that are capable of running TPM 2.0 are not set up to do so. If you are considering upgrading to Windows 11, check to ensure TPM 2.0 is enabled on your device.