This error message typically arises when attempting to forward an email to an address that exists in an older, incompatible format. Specifically, the sending system is unable to translate the recipient’s address from the modern format used by the current Exchange environment to the older, proprietary format utilized by legacy Exchange systems. This often occurs when the recipient address is stored in the sender’s contacts or auto-complete cache as an “Exchange Legacy DN” (Distinguished Name). For example, an address might appear as “/O=ORGANIZATION/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=USER” instead of a standard SMTP address like user@domain.com.
The significance of understanding this issue lies in ensuring seamless email communication within and outside organizations that have undergone Exchange server upgrades or migrations. Addressing the underlying cause prevents disruption in workflow and maintains the integrity of email correspondence. Historically, this problem was more prevalent during transitions between different versions of Exchange. While modern Exchange systems are generally designed to handle a mix of legacy and current address formats, outdated client software or improperly configured address books can still trigger this error. Mitigating it often involves updating the recipient’s address to the current SMTP format or using tools to cleanse legacy address information from the system.
