Are you sure that your address is not blocked by "blacklists" or that the server hosting your site has not been hacked?
It happens to everyone sooner or later to send an e-mail and deal with it blocked by a spam filter. Usually, those who send newsletters and e-mail marketing campaigns for work notice this when they send a test email to the customer and the latter, after a few hours, claims that he never received it. Thus, it often turns out that the carefully crafted e-mail has been considered spam and ended up in the junk mail folder.
That of the customer, of course.
Servers that are not properly configured or that are “compromised” by attacks are seen by the rest of the internet as unreliable servers and therefore the e-mail messages sent by these servers tend to be rejected or stopped by the recipient's antispam.
Request a free check about your situation with the hosting service you are using clicking here or call 392 035 33 86 directly