My dad used to self-host email for his company. It worked fine for a long time -- until MS started silently discarding his emails. A lot of his clients (very l

My dad used to self-host email for his company. It worked fine for a long time -- until MS started silently discarding his emails. A lot of his clients (very large companies) use MS for email, and his emails to them got silently discarded (not rejected as spam, not showing up in spam folder, simply discarded while responding that the email had been accepted). Notably, the invoices he was sending didn't reach the intended inbox, so he eventually had to move on to use another provider for email. I've heard this story dozens (if not hundreds) of times over the last couple of decades. It gets worse and worse, since huge corporations only whitelist other huge corporations, and can choose to blacklist the rest. The oligopoly has won.