This is a question that comes across my desk from time to time, when a client want to send emails with attachments to their customers. Sometimes it’s a receipt, an order form or a update to an existing contract or service, or sometimes people just want to send something as an attachment to all of their customers. Typically I would not recommend this type of program be sent from an ESPs platform as they are not generally setup to handle these request without some type of customization, the message size is often a factor in slower mail delivery and in some cases delivery issues.

Before considering any type of deployment requiring an attachment think about these factors:

      1 – Message size – many corporate spam filters limit the attachment size in emails, also mail box size limitations for some individuals. may not be as big of an issues for some webmail recipients.
      2 – The largest spam attacks currently under way are delivering Ransom Ware and other malware to individuals trying to infect their PCs.
      3 – Consumer trust, because of #2 consumers trust in attachments are very low – even from trusted brands.
      4 – Tracking – unable to track who opens the attachment, but you can track who clicks the link to download/view a landing pages.
      5 – Delivery speeds, large messages with attachments are much slower than messages with links to download the file.

When considering adding attachments in email be sure to consider all the options and the alternatives to help improve both delivery and the user experience of your recipients.

Sources of information:
National Cyber security
TrendMicro(Popular Anti-spam appliance)
Get Cyber Safe; Sections: 4.4 , 4.7, 6.1