Despite the efforts that eNotify makes to ensure eNotices don't get caught in spam filters, there will still be some filters—either by default or due to user settings—that handle emails with a "when in doubt, throw it out" philosophy. Recipients may allow emails only from a predetermined "white list" of senders, in which case, you will need to contact the recipient via snail mail or phone call and request that your newsletter's "From" address be added to that white list.
The emails are seen as coming from whatever "From" address you specify in eNotify. By default it would be your email address, unless you specified an alternate "From" address using the Sender Address Manager feature. Ask the recipient to "whitelist" this email in their email client (or add to their address book) to be sure they receive your eNotify messages.