That's false positive from the SPAM filter.
For the message in the spam folder.
Mark them as non-spam/acceptable. That should cause them to be placed back in your inbox. It should also allow similar messages to stay in the inbox.
You may want to use another e-mail app. You can always install one of your choice.
Some times, e-mails can get blocked on the server before you ever see them. In this case, your only option option is to use another e-mail service.