Deliverability Compliance & Bounce Rules
Automate compliance with Yahoo and Google sender policies. Inject unsubscribe headers, handle hard bounces, and maintain a secure suppression list.
Compliance stopped being optional when Google and Yahoo turned their bulk sender guidance into enforced requirements. This module implements those obligations, and handles the bounce and suppression mechanics that keep a sending domain usable over time.
One-click unsubscribe is a header, not a link
The requirement most senders fail is this one, because a visible unsubscribe link in the message body does not satisfy it. What is required is a header-level mechanism letting the recipient opt out from inside their mail client in a single action. That needs two headers: List-Unsubscribe carrying an HTTPS endpoint, and List-Unsubscribe-Post declaring that the endpoint accepts a POST and will act on it without further interaction. The second is the one commonly omitted, and without it the native unsubscribe control simply does not appear. Both are added to every campaign automatically.
Why suppression entries are stored as hashes
When someone asks not to be contacted, retaining their address in readable form to remember that request is an uncomfortable contradiction. Entries are stored as SHA-256 hashes instead. An outgoing address is hashed and compared, so the suppression is enforced reliably on every future campaign - including lists imported months later - without keeping readable contact data for a person who has already opted out.
Soft and hard bounces need opposite handling
A hard bounce returns a 5xx code and means the address does not exist. It is suppressed permanently and never retried; retrying is both pointless and a signal to the provider that you are not processing their responses. A soft bounce returns 4xx and is temporary - a full mailbox, a server briefly down - and is retried on a widening backoff before being escalated. Treating these identically is one of the more common causes of avoidable reputation damage.
Catching the bounces that arrive after the send
Not every bounce happens during the SMTP conversation. Gmail and Microsoft frequently accept a message, then discover minutes later that the mailbox does not exist and send a Non-Delivery Report back to the sending mailbox. A platform that only reads the SMTP response never sees these, so it reports the address as sent and mails it again next time. Email.biz.pk also checks each connected sending mailbox for these reports, suppresses the addresses they name, and corrects the campaign's bounce count. It reads delivery reports only and never alters the mailbox — nothing is marked read, moved or deleted.
What a custom tracking domain actually buys you
Open and click tracking works by rewriting links so they resolve through a tracking host first. On a shared tracking domain, that host's reputation is the aggregate of everyone using it. A custom CNAME tracking domain means your links resolve on your own subdomain, so the reputation attached to them is yours alone - and cannot be damaged by another sender you have never met.
Feature Breakdown
RFC 8058 One-Click Unsubscribe
Injects standard list-unsubscribe headers into every message, allowing recipients to opt out directly through their email client.
Technical Capabilities:
Global Workspace Suppression List
Maintains a database of opt-outs and hard bounces to prevent you from emailing them again.
Technical Capabilities:
Bounce Management (Soft & Hard)
Classifies bounces automatically to prune bad email addresses and retry temporary delivery failures.
Technical Capabilities:
Isolated Custom CNAME Tracking Domains
Ensures your tracking links use your own subdomain, protecting your brand reputation from other platform users.
Technical Capabilities:
Attribution Header Injection
Adds required headers to verify email authenticity and support ISP feedback loops.
Technical Capabilities:
Spec Sheet
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Deliverability Compliance & Bounce Rules questions.
The specifics people ask about before relying on this part of the platform.
Do you support one-click unsubscribe?
Yes. Every campaign includes an RFC 8058 List-Unsubscribe-Post header, which Gmail and Yahoo now require from bulk senders. A recipient can opt out in one action without leaving their inbox.
How are unsubscribes and bounces handled?
Both are added to a workspace-wide suppression list and excluded from every future campaign automatically. Entries are stored as SHA-256 hashes, so opt-outs are honoured without retaining a readable copy of the address of someone who asked not to be contacted.
What is the difference between a soft and a hard bounce here?
A hard bounce means the address does not exist and is suppressed permanently — whether the receiving server rejected it during sending or returned a delivery failure report afterwards. A soft bounce is a temporary failure such as a full mailbox, and is retried on a backoff schedule rather than suppressed, so a real contact is not lost to a passing problem.
Why would I use a custom tracking domain?
Tracking links on a shared domain inherit the reputation of everyone else using it. A custom CNAME tracking domain means your open and click links resolve on your own subdomain, keeping that reputation isolated to you.