They are actually one of the few services that u can use for programmatically receiving emails. When it works, it just works - but unfortunately the spam thing bit us as well.
Fortunately we were able to get it resolved quickly
I use MG for automated email intake too, but I also use sparkpost as a backup email intake.
How do you switch from the primary to the backup?
for our purpose i have two distinct email domains and fwd to both addresses and process which ever hits my servers first.
We provide that at Twilio SendGrid too: Parse Webhook
Having both phones and email at one supplier sounds risky. If you lock my account it takes out the two major ways a customer can reach us. No thanks.
They provide MX forwarding for delivery, but we use them because it saves us from having to buy a per user email account with gsuite or outlook. It's a little bit of a hassle/hack, but it works well enough in practice. I use a free gmail account that receives forwarded emails from Mailgun, and I can respond via mailgun smtp within gmail.
If I remember right, they recommend using a sub domain and being an Mx.