Currently, individuals who are off-campus and attempting to send email via the campus email servers over a third-party ISP connection are limited to sending mail only to campus email addresses. This limitation is due to the security risks involved in allowing these "open relays," which have been disallowed on campus since 1997.
In most cases, users will be required to change a setting in their email program to enable authenticated SMTP. Support documentation will be available to assist users in making this change. A plan is also being developed for announcing the availability of this new email option for off-campus affiliates and "commuters." For additional information, see security.ucdavis.edu/openmailrelay.cfm.