The information on this page is to help you if you are having problems sending mail to Oxford users.
Receiving a bounce
550 Mail transactions must start with EHLO/HELO
RFC2821 s22.214.171.124 a client MUST issue HELO or EHLO before starting a mail transaction
Configure your server to use the EHLO or HELO command before MAIL.
550 Invalid HELO (foo) used by 192.168.4.90
RFC1123 s5.2.5 The sender-SMTP MUST ensure that the <domain> parameter in a HELO command is a valid principal host domain name for the client host RFC2821 s126.96.36.199 The argument field contains the fully-qualified domain name of the SMTP client if one is available. In situations in which the SMTP client system does not have a meaningful domain name (e.g., when its address is dynamically allocated and no reverse mapping record is available), the client SHOULD send an address literal (see section 4.1.3), optionally followed by information that will help to identify the client system.
Configure your server to give either its Fully-Qualified Domain Name or IP address literal as the argument to the EHLO or HELO command.
550 Verification failed for <email@example.com>
The sender domain must exist and have valid DNS records.
Not receiving a bounce
It is possible the Oxford user has filtered your message into their junk-mail box. Ask the user to check, and add your sender address to their whitelist if appropriate.