Target platforms block known disposable email domains (`tempmail`, `guerrillamail`) and also flag custom domains that use cheap shared mail hosting MX records. Here is how to make your custom aged `.com` domains look like legitimate corporate Google Workspace or Microsoft 365 domains: 1. **Subdomain MX Delegation**: Point root `@` MX to Google/Cloudflare or a clean IP, and route a subdomain or SMTP relay via Postfix `virtual_alias_maps` catch-all. 2. **Strict DNS Auth**: Publish `v=spf1 -all`, 2048-bit `DKIM`, and `v=DMARC1; p=reject` records—signup fraud engines query DNS TXT records in real time during registration!