This approach is, of course, fixing the symptom and not the disease. Header verification Exim's sender verification options can be used to block messages with bad envelope senders. If there are several occurrences of any of the relevant headers, they are all checked. This is a syntax check only. Receiver verification By default, Exim just checks the syntax of addresses given in the SMTP RCPT command.
Some installations prefer to check receiver addresses as they are received.
If verification fails, a permanent negative response is given to the RCPT command. Go to the first , previous , next , last section, table of contents .