Some emails not reaching the recipient; no error messages or bounce-backs

I have a program that takes a 100+ page PDF file and sends 100+ emails to various recipients, each of whom receives a different page of the PDF as an attachment.  Each week, a dozen or more recipients don't get the email--it's not always the same recipient, nothing bounces back, and there are nothing in any of the local logs to indicate a problem.  I've reviewed the quotas in http://businesshelp.comcast.com/help-and-support/E​mail/email-size-storage-limits/  and if that's the problem I have no way of knowing it.  How can I find out if this issue is related to the Comcast outgoing mail Server?  Thx in advance .... DMiller