"The '-s' option means subject; the '-S' option is a keyword:value pair."
Rich - See example 6: 6. Specify "Reply-To" address The reply to address is set with the internal option variable "replyto" using the "-S" option. # replyto email $ echo "This is message" | mail -s "Testing replyto" -S replyto="m...@gmail.com" some...@example.com # replyto email with a name $ echo "This is message" | mail -s "Testing replyto" -S replyto="Mark<m...@gmail.com>" some...@example.com
