Most hosting providers block SMTP by default. They enable SMTP on servers after we drop them a mail. It can take up-to a week to get these approvals.
Considerations when choosing a host:
- Allows reverse DNS
- IPs are whitelisted
Hosting providers that allow reverse DNS:
Hosting providers that don't allow reverse DNS:
- DigitalOcean doesn't allow reverse DNS on elastic IP.
Most hosting providers provide an option of elastic ip which can be attached to a server. These IPs are usually whitelisted.