A few days ago we started no longer receiving order notifications to our email addres

Using version 1.3.9h
Did the update about 5 months ago.
No problems or issues since updating, and no add ons, or changes at all since updating 5 months ago.

A few days ago we started no longer receiving order notifications to our email address. The PayPal notifications also have been either very much delayed or do not come at all. The orders can be seen on our ZenCart admin page, but no email notifications. I see that others have similar problems starting about the same time as ours started, a couple days ago, so it's not something we did and must be something going on in ZenCart.

goldnuggetsales.com:

so it's not something we did and must be something going on in ZenCart.
The software sits on your own server, and is solely in your control. When you download and install the Zen Cart application (or use somebody's 1-click install), it's yours. Period. Zen Cart as an organization has NO access to your site, your data, your server, etc.

So, if something's suddenly stopped working properly with software on your server, then you need to be looking at whatever's been changed on the server ... either in your files (addons added, files edited, hacker activity in your files) or in your webserver (managed by your server admin, typically someone at your hosting company).

So how is it possible that quite a few people are reporting the same problem starting at exactly the same time? Any ideas on what might be causing it are how to find the source of the problem? I for one have not made a single change to any files, no add ons, nothing. I haven't touched anything on the server since upgrading 5 motnhs ago. If I was the only one with this problem I could understand but several threads with the same problem started at the time our problem started.

And each person's individual case appears to have symptoms unique to their own situation.
You need to research your specific cause directly. Recreate the problem, find out what patterns exist to trigger the problem, discover what errors are occurring in the background, etc.

I just found the missing orders in my email spam folder, along with some email requests from the website also. I have never had that happen before. Wonder if the other people having the same problem will also find their missing orders in their spam folders?

It's certainly one possible answer that should be investigated if somebody's not receiving mail. But for others reading this, there are many other ways for mail to go astray that should be considered as possibilities too.

goldnuggetsales.com:

I just found the missing orders in my email spam folder, along with some email requests from the website also. I have never had that happen before. Wonder if the other people having the same problem will also find their missing orders in their spam folders?
That suggests that the problem lies in a change to whatever system sets the junkmail flag on emails. So, that would be a setting on one of the servers involved in delivering the email to you. ie: It's very possible that one or more of the servers handling delivery has had its spam detection settings changed by the server administrator.

Simply changing Admin->Configuration->Email Options->Email Transport Method from "PHP" to "SMTPAUTH", and setting the SMTP credentials on that same screen, is often enough to limit the spam trigger because SMTPAUTH sends emails as authenticated by the sender, and not as an anonymous "nobody" via a generic PHP configuration typically abused by spammers.

http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Email_Problems
http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Understanding_Causes_Of_Lost_Emails