Problem s pošiljanjem mejla

Ko pošljem mejl z Arnesovega accounta mi pošlje v redu. Ko pa naprimer iz Telemachovega ali kakega drugega, mi pa vrne mejl z vsebino:

Your message did not reach some or all of the intended recipients.

Subject: fgreger
Sent: 12.1.2004 11:31

The following recipient(s) could not be reached:

'yeznick@email.si' on 12.1.2004 11:31
554 yeznick@email.si: Relay access denied


V čem je problem?

sem probal oba:
mail.telemach.net in smtp.telemach.net