If an airline cancels my boarding pass because they don't like my email address (?), too bad for them, they just lost a sale.
If someone keeps missing important emails because their provider's spam checker isn't very good, that's not my problem.
Although I have to say that I don't run into these situations very frequently, and I use a basic postfix/dovecot setup on a VPS for my mail.
Trust me, they don't care, I say this from experience. They don't seem to even have insight into these bans or the volume they're happening in. I had to spam Amazon support on and off for two years to get my account unlocked. And we all know how much Amazon cares about the customer... pah.
Standing your ground as a customer doesn't do anything but make life a misery.
Sure but now you can't get home. I travel a ton, and this would be a major issue for me. You can't always just get on a different plane. Lucky you i guess, but airlines are one of those things that most people can't mess with.
I think it's delusional to think they care any more than you do.