If this setting is included in the NOTES.INI file, it overrides the DNS value.
SPR# RSNR463NER - Prevent the POP3 task initialization from failing when a setting is missing. Previously, POP3 failed to load if a POP3Domain environment variable was not set in the NOTES.INI. The POP3Domain value is now just an override on the Domain Document's setting, if it exists. If neither the Domain Document nor the variable are set, the IMAP default of "NoInternetDomain" is used. [5.0.1]