The vocabulary,
decoded.
DKIM, DMARC, BIMI, MTA, EHLO, idempotency keys, spam traps. Every term you'll encounter while operating an email program — defined, exemplified, cross-linked.
B
BIMI
Brand Indicators for Message Identification
A DNS TXT record that authorises an SVG logo to render next to your sender name in supported inboxes. Requires a DMARC policy of quarantine or reject and (for Gmail/Apple) a Verified Mark Certificate.
Bounce rate
Percentage of sends that the receiving MTA refused. Hard bounces are permanent (invalid address); soft bounces are temporary (full mailbox, server down). Above ~3% sustained, ISPs throttle or quarantine your domain.
D
DKIM
DomainKeys Identified Mail
Cryptographic signature added to email headers. Receivers fetch the public key from DNS and verify that the message body has not been altered. VoltMail rotates DKIM with two selectors so rotation is zero-downtime.
DMARC
Domain-based Message Authentication, Reporting & Conformance
Policy record sitting on top of SPF + DKIM. Tells receivers what to do when both fail (none / quarantine / reject) and where to send aggregate or forensic reports.
H
HIPAA BAA
Business Associate Agreement
Contract between a covered entity (a hospital, insurer, etc.) and a vendor that handles Protected Health Information. VoltMail offers a BAA on Pro Max with HIPAA-conformant infrastructure.
HMAC
Hash-based Message Authentication Code
Symmetric signature scheme. Every VoltMail webhook delivery carries an X-VoltMail-Signature header containing an HMAC-SHA256 over (timestamp + body). Verify it before trusting the payload.
I
Idempotency key
A client-generated identifier passed in the Idempotency-Key request header. We cache the (key, response) pair for 24 hours; identical retries return the same response without performing the work twice.
IP warming
The process of slowly building reputation on a brand-new dedicated IP by sending small, gradually-increasing volume. Skipping the warm reliably parks new mail in spam for weeks. Our auto-warm doubles every 36 hours.
M
MTA
Mail Transfer Agent
Software that accepts mail over SMTP and routes it. Postal, Postfix, and Exim are MTAs. VoltMail runs a Postal cluster in production with custom queue + retry logic.
MX record
A DNS record listing the mail servers responsible for receiving mail at a domain. Outbound senders look up the MX, then connect to the highest-priority host.
S
Spam trap
An email address used to catch senders with poor list hygiene. Pristine traps were never opted-in; recycled traps were once valid but now expire. A single hit can damage your reputation for weeks.
SPF
Sender Policy Framework
A TXT record that lists the IPs authorised to send mail "from" your domain. Receivers reject mail whose source IP is not in the list.
Suppression list
A per-account record of email addresses that should never receive mail again — typically populated by hard bounces, complaints, and unsubs. We maintain a global list across all of your sending domains.