web1 ~ # sendmail -v valid@email.com
asdasd
[<-] 220 wellington.concentric.com [ConcentricHost ESMTP Relay 2/2.54] ready
[->] HELO web1
[<-] 250 wellington.concentric.com
[->] MAIL FROM:<root@web1>
[<-] 250 Ok
[->] RCPT TO:<valid@email.com>
[<-] 504 <root@web1>: Sender address rejected: need fully-qualified address
sendmail: RCPT TO:<valid@email.com> (504 <root@web1>: Sender address rejected: need fully-qualified address)