First ensure "logging event link-status" is configured globally or per-interface on the "interesting" interface. Then configure something similar to the following:
event manager environment _email_to recipient@domain.com
event manager environment _email_server smtp.domain.com
event manager environment _email_from sender@domain.com
event manager applet interfaceDown
event syslog pattern “.*UPDOWN.*TenGigabitEthernet1/0.*changed state to down”
action 1.0 mail server "$_email_server" to "$_email_to" from "$_email_from" subject "$_event_pub_time: TenGigabitEthernet1/0 interface down" body "$_event_pub_time: TenGigabitEthernet1/0 interface down"