Information Systems & Services (ISS) - Rejected Mail

Information Systems & Services (ISS)

Spam - Rejected Mail

We use postfix to block a large number of spam mails to DCU every day. Ocassionaly genuine mail will get blocked. There can be a number of reasons for this but in general you should contact your own mail administrator/provider.

If you send a mail which gets rejected you will receive a reject message. This explains why your mail was blocked. This information will be needed by your mail administrator to determine what the problem is.

Sample Reject Messages

Dangerous Attachments - more info

    Your message contained an attachment which is considered potentially dangerous.
    Please see
    This contains instructions on how to send these file types to DCU mail accounts.

DNS Blacklists blocking - more info

    Service unavailable; Client host [999.888.777.666] blocked using;
    Blocked - see (in reply to RCPT TO command)

Helo Command Rejected - more info

    RCPT TO: <> Received 504 <MachineName>:
    Helo command rejected: need fully-qualified hostname

Don't understand why your mail to DCU is being rejected ?

If you have found none of the above helpful we can examine your reject message.
You will need to go to this page and enter the reject message in the form provided.