Having run business email servers since the 90's and having our employees not receive emails (critical things like Direct Deposit Notifications), I am wondering if the problem is with your email service provider, especially if your email address is through a cable company.
Cable companies are always looking to filter out spam as a "feature" to sell themselves to you the user. Unfortunatly spam filters are rather stupid and don't know that what might be junk to some is a treasure to you.
Having had many of these cable providers on the phone over the years trying to help our employees get their emails, I can tell you that they are interlinked. Once a site gets blocked on one, it gets spread to others. We had payroll all over the country (40+ states), so it was a pain.
If kalmbachmail.com gets reported as spam, each of these counts as a complaint and counted. When a magic number gets reached, they get cut off and that block gets reported up and down the country to other cable/mail providers that subscribe to the same filter service and you have a cascading issue. NOTE: There are other triggers besides complaints that are counted and used to up your "spam score" that will get you blocked.
When I say that spam filters are stupid - we were a Temporary Placement Service that sent resumes to our clients base on their needs and requests. We once had a client that couldn't get emails from us and their experts couldn't figure out why. The nearest answer was that they were looking for piping designers. Piping Designer resumes would refer to "nipple fittings" and that triggered our server getting blocked. I could go on and on...
With all the email Kalmbach sends out (volume is also a negative in the scoring system) and all the crazy analysis criteria that spam filters use, it is no surprise to me that many of your emails get blocked at times.