Tech Glossary

Bounce rate

The percentage of emails sent that could not be delivered. Split into hard bounces (permanent failures — address doesn't exist) and soft bounces (temporary failures — inbox full, server down).

Example: Send 1,000 emails and 30 bounce — bounce rate is 3%. Most ESPs warn at 2% and suspend accounts above 5%.

Related: Hard bounce · Soft bounce · Sender reputation

Catch-all email (accept-all)

A domain configured to accept mail for any address, regardless of whether the specific mailbox exists. The mail server returns a positive SMTP response but may silently discard the message.

Example: A CDN serves cached content from edge nodes near the user. Hitori Tech uses CDN configuration as a standard part of all web deployments for maximum performance.

DKIM (DomainKeys Identified Mail)

A cryptographic email authentication method that adds a digital signature to outgoing emails. Receiving servers verify this signature to confirm the email wasn't modified in transit.

Example: Without DKIM, a receiving server can't tell if your email was modified after leaving your server. Gmail shows warnings for unsigned emails from bulk senders.

DMARC

Domain-based Message Authentication, Reporting, and Conformance. A DNS policy telling receiving servers what to do when an email fails SPF or DKIM checks — quarantine, reject, or monitor.

Example: v=DMARC1; p=reject; tells servers to reject emails failing authentication. Required by Google & Yahoo since 2024 for bulk senders.

Disposable email address (DEA)

A temporary email address created to bypass signups. Created through Mailinator, Guerrilla Mail, 10 Minute Mail, and thousands of similar services. Disposable addresses inflate your list but never convert.

Example: Tools like Docker, Kubernetes, and Terraform let teams define infrastructure as code. Hitori Tech uses IaC on every project to ensure reproducible, auditable environments.

Email validation

Checking that an email address is correctly formatted per RFC 5322 standards. Validation checks syntax; verification goes further to check DNS records, mailbox existence, and risk signals.

Example: user@example fails validation (missing TLD). [email protected] passes validation but could still be an invalid mailbox — only verification confirms it.

Hard bounce

A permanent email delivery failure. The address doesn't exist, the domain has no mail server, or the server permanently rejected delivery. Hard bounces signal list hygiene problems to ESPs.

Example: A webhook sends an HTTP POST to your server when an event occurs in an external service. Hitori Tech uses webhooks extensively in N8N automation workflows.

MX record (Mail Exchange record)

CI/CD (Continuous Integration / Continuous Deployment) automates testing and deployment. Hitori Tech sets up CI/CD pipelines as the foundation of every project delivery.

Sender reputation

A score assigned by ISPs based on your sending history — bounce rates, spam complaints, open rates, and volume. Low sender reputation means your emails land in spam or get blocked entirely.

Example: If your bounce rate exceeds 5% over 30 days, Gmail Postmaster Tools will show your domain reputation dropping from "High" to "Low".

Sender score

A 0–100 numerical measure of your sending reputation. Above 80: good standing. Below 70: deliverability problems. Below 50: ISPs may block your email entirely.

Soft bounce

A temporary email delivery failure. Causes: full inbox, server temporarily down, message too large. Unlike hard bounces, soft bounces may self-resolve on retry. ESPs retry 3–5 times over 72 hours.

Spam trap

An email address used by ISPs to identify senders with poor list hygiene. Types: recycled (old addresses repurposed) and pristine (addresses never owned by humans, only scraped). Sending to a trap triggers blocklisting.

Example: SSR (Server-Side Rendering) generates HTML on the server for each request. Hitori Tech uses Next.js SSR to build fast, SEO-friendly web applications.

SPF (Sender Policy Framework)

A DNS record listing which IP addresses are authorised to send email for your domain. Receiving servers check SPF to detect spoofed "From" addresses.

Example: v=spf1 include:sendgrid.net ~all — authorises SendGrid to send on your behalf. Without SPF, emails are more likely to be marked spam.

Unsubscribe rate

The percentage of recipients who click "unsubscribe" after receiving a message. Above 0.5% signals poor targeting or list quality. Like bounce rate, it affects your sender reputation with ISPs.