What sharing an address means for your mail.
HOW RECEIVING PROVIDERS JUDGE MAIL
They weigh the sending IP's history, the domain's authentication records, the content, and engagement signals from recipients.
The IP's history is aggregate: everyone sending from that address contributes to it.
THE RISK
If another account on your shared address is compromised and sends spam, the address can be listed on blacklists. Your legitimate mail then encounters filtering until the listing is resolved.
WHAT WE DO
Monitor outbound mail, enforce per-account hourly sending limits, act on compromised accounts, and handle delisting of server addresses.
WHAT YOU CAN DO
Make sure SPF, DKIM and DMARC are correct under cPanel > Email Deliverability. Well-authenticated mail from a properly configured domain survives a marginal IP reputation far better than unauthenticated mail. Send from an address on your own domain. Use authenticated SMTP rather than PHP mail. Move bulk sending to a dedicated provider.
IN PRACTICE
For most businesses sending ordinary correspondence, a shared address is entirely adequate.
