It doesn't matter that some mail from them makes it. Due to the insane amount of spam there are so many filters on mail servers today that mail, as we know it is not reliable. This can really upset those that want to know why email doesn't work under some conditions and then works again.
If you need such information the investment company I use has my own login which has those reports for pickup at their site. Again, the why is all about email being unreliable. It used to be reliable but today, I hate to break it to those unaware of the issues but you just can't count on it.
I requested some specific end of month historical investment information from an investment company and they had to have their research group look up the data and then send it to me in an encrypted email. After 3 or 4 days I did not receive any email. I called them and the rep said that the research group had logged in that they had in fact sent an email to me 2 days earlier. She submitted a request to them to send it again. Two days later, still no email I called again and the new rep checked and saw that they had sent it twice, but it did not come through to my email. He sent one of the reports on the spot and after waiting for 5 minutes, no email. I asked him to send it to my Gmail address (the other emails were sent to my Comcast account for which I use Mozilla Thunderbird) which also did not receive his email after 4 or 5 minutes.
All of this leads to me to believe that something has happened to a setting outside of either email app, possibly something with an antivirus or malware app I am using. I use Avast for antivirus and Malwarebytes for malware capture. But I also am wondering if the encryption they use is interfering with some security feature on my PC (Windows 10). This is the only company that is creating this problem with my system, which makes me think maybe I accidentally labeled them as a "junk" mail sender, but if I did, they would show up in the Junk folder in my email apps, which they do not.
BTW, this has has happened only once before back in May of this year, and when it happened, the second rep I talked with was able to send the report directly to me and it showed up in just a minute or two.
I should also mention that when the company sends emails such as newsletters or other notices to all customers, I do receive them.
Any ideas on what might be happening?