For my solo SaaS company:
Backups:
- Backblaze (disaster recovery for my laptop)
Hosting:
- Cloudflare Workers
- fly.io (actually free when under $5/mo usage but I wish I was giving them money)
- AWS
Emails:
- Postmark
After messing around with emails that weren't being received (especially with email-only auth), glad I found Postmark
- Gsuite
- Dmarc Reports
Monitoring to see if I configured Dmarc correctly everywhere