Firstly, all of the recipients' addresses were in the To: field.
Secondly, it was a MIME message with three parts. The first part was HTML:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1491" name=GENERATOR></HEAD> <BODY> <DIV> <TABLE cellSpacing=0 cellPadding=0 width=600> <TBODY> <TR> <TD><IMG height=327 src="http://www.webnet-recruitment.com/email/microcom/cand05.jpg" width=600></TD></TR> <TR> <TD><IMG height=273 src="http://www.webnet-recruitment.com/email/microcom/cand04.jpg" width=600 border=0></TD></TR> <TR> <TD height=214> <P align=center><FONT face="Arial, Helvetica, sans-serif" color=#0033ff size=1><BR>This email was sent to you as a registered candidate with Microcom Ltd. If you do not want to receive future communications from our database please email to firstname.lastname@example.org and we will remove you from our databases.</FONT></P> <P><FONT face="Arial, Helvetica, sans-serif" size=1>The views </FONT><FONT face="Arial, Helvetica, sans-serif" size=1>expressed in this e-mail are not necessarily the views of Worldwide Recruitment Holdings Ltd, its directors, officers or employees make no representation or accept any liability for its accuracy or completeness unless expressly stated to the contrary.<BR>This e-mail, and any attachments are strictly confidential and intended for the addressee(s) only. </FONT></P> <P><FONT face="Arial, Helvetica, sans-serif" size=1>The content may also contain legal, professional or other privileged information. Unless expressly stated to the contrary, no contracts may be concluded on behalf of Worldwide Recruitment Holdings Ltd by means of e-mail communication. You may report the matter by calling us on +44 (0) 1727 752000.</FONT></P> <P><FONT face="Arial, Helvetica, sans-serif" size=1>Please ensure you have adequate virus protection before you open or detach any documents from this transmission. Worldwide Recruitment Holdings Ltd does not accept any liability for viruses. </FONT></P> <P><FONT face="Arial, Helvetica, sans-serif" size=1>Worldwide Recruitment Holdings Ltd is registered in England: Company number: 0391174.<BR>Registered Office: Faulkner House, Victoria Street, St Albans, Herts, AL1 3SE.</FONT><BR></P></TD></TR></TBODY></TABLE></DIV></BODY></HTML>
The other two parts were the referenced jpeg files: