Hi, Does anybody know what the following smtp error message means and how do I fix it. #5.5.0 smtp;553 sorry, envelope sender must have a valid domain name (#5.7.1) Many thanks Simon Whale ----------------------------------------------------------------------- This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify admin@xxxxxxxxxxxxxxx The views expressed in this email are those of the individual and not necessarily those of UK Data IT This footnote also confirms that this email message has been swept by SOPHOS AV for the presence of computer viruses.