Email forwarding architecture: envelope, header, SRS, and delivery hops

Quick answer for email forwarding architecture

Publish exclusive MailerZ MX. Create named aliases. Probe so hop three and four leave a trail. Keep Header From intact. Let SRS handle the envelope. That is email forwarding architecture.

Guide: name hops in tickets. Setup: leftovers first. Best practice: no Header-From rewrite, no self-send, no backup leftover host.

Hop five is paid SMTP. Free has no hop five.

Open relay is not this architecture. Unauthorized send is 550 / 550 5.7.1.

MailerZ Free is one domain, ten aliases, one seat, a 14-day store, send-as disabled, SMTP and API disabled, and unrouted mail held or rejected only. Solo is $40 per year only. Starter is $8 monthly or $80 yearly. Business is $19 or $190. Agency is $39 or $390. Unlimited is $99/month or $990/year. Confirm numbers on MailerZ pricing. Limits are not an inbox-placement promise.

Google’s own Send mail as steps live in Google Gmail Help — Send mail from a different address. Workspace as a product is described on Google Workspace — product overview. Transport still follows IETF RFC 5321 — Simple Mail Transfer Protocol.

email forwarding architecture guide: the real decision

Dashboards show hop two while hop one is Google.

Products that rewrite Header From call themselves forwarding.

Agencies share leftover MX across clients and call the architecture flaky.

Criteria: exclusive MX, intact headers, SRS envelope, named hops, probe evidence.

Technical mail flow for email forwarding architecture

Resolver, preference order, accept, map, SRS envelope, second session, destination classify, optional new outbound.

Preference is an order. Leftover better-preference host steals hop one.

Unknown policy is hop two. Hold on Free.

Reply is not a forward. It is hop five.

MailerZ is inbound MX plus authenticated SMTP from Secuno LLC. Envelope SRS only. Header From, Subject, Date, Message-ID, body, and MIME are never rewritten. Not Google Workspace, not IMAP or POP, not an open relay. Unauthorized send is SMTP 550 / 550 5.7.1. Leftover MX is a hard stop. Self-send from Gmail to the same Gmail account can hide routing errors. Not SOC 2, not ISO 27001, not HIPAA.

email forwarding architecture setup

Draw the hops. Then publish only one MX set.

1. Check NS, then MX, from two public views.
2. Verify the domain.
3. Create named aliases.
4. Publish MailerZ MX. Delete leftovers.
5. Probe with a unique subject from another mailbox.
6. Read history (hop three) and the store (hop four).
7. Attach send-as only if hop five is required.
8. Write hop numbers into the runbook.

Failure modes and proof

Header-From rewrite product.

Backup leftover MX.

Self-send as architecture proof.

Catch-all as the map.

Shared leftover across clients.

MailerZ workflow and product boundary

Envelope SRS only. Header From, Subject, Date, Message-ID, body, MIME never rewritten. Related: email forwarding, features, delivery recovery, email routing lab.

Not IMAP. Not a suite. Not an inbox SLA.

Related pages: email forwarding, features, delivery recovery, and email routing lab.

email forwarding architecture best practice

Free proves hops one through four on one domain. Solo starts hop five. A VPS makes you the hop-three pager. A suite replaces the store. Confirm pricing.

Wrong aisle costs more than Agency.

MailerZ Free is one domain, ten aliases, one seat, a 14-day store, send-as disabled, SMTP and API disabled, and unrouted mail held or rejected only. Solo is $40 per year only. Starter is $8 monthly or $80 yearly. Business is $19 or $190. Agency is $39 or $390. Unlimited is $99/month or $990/year. Confirm numbers on MailerZ pricing. Limits are not an inbox-placement promise.

Field notes you can reuse

Cite RFC 5321 and RFC 5322 by role, not as decoration.

ARC is evidence, not a folder promise.

Hold unknowns at hop two.

Agencies: per-zone hop one.

Forms are hop five if they send as the domain.

Delivery recovery is hop-three storage.

Quarterly leftover review.

The how-it-works page is the sequence in story form. This page is the contract between envelope and header.

Deeper field notes for email forwarding architecture

Envelope is RFC 5321. Header is what humans read.

Email forwarding architecture is a second SMTP transaction. The first accept uses your MX. The second delivery uses a destination mailbox. Envelope MAIL FROM may change (SRS) so the hop that talks to Gmail can pass SPF. Header From should stay the original author. MailerZ’s boundary is that split. Rewrite the header and you have a different architecture with a worse DMARC story.

RCPT TO on hop one is the public alias. RCPT TO on hop two is the Gmail or Outlook address. Confusing those is how people paste a Gmail password into a forwarder and call it MX. The map is the architecture. The store is not the domain.

SRS is not a From change

Sender Rewriting Scheme changes the envelope so bounces and SPF at the destination describe the hop that actually sent. It does not change the name the human sees. Teams that “SRS the visible From” are not doing SRS. They are rewriting Header From. Stop. Cite the envelope. Leave the header.

Hops you can name in a ticket

Hop one: public MX. Hop two: alias map and unknown policy. Hop three: second SMTP and this layer’s history. Hop four: destination classify. Hop five: optional send-as, a new message. Architecture setup is standing them up in order. Architecture best practice is naming the dead hop instead of opening every dashboard.

Leftover better-preference MX ends the story at hop one. Hold ends unknown names at hop two. Destination reject ends some copies at hop three or four. Self-send skips the sequence and lies about all of them.

What this architecture refuses

Open relay. IMAP. Webmail. Header rewrite. Inbox SLA. SOC 2 theater. Unauthorized send is 550 / 550 5.7.1. Free has no hop five. The 14-day and 90-day stores are hop-three recovery windows, not an archive architecture.

Compare Cloudflare routing (inbound, limited send story), a suite (hosted mailbox), Proton (encrypted store), a privacy mask (provider domain). Cite their docs. MailerZ is the delivery layer when you already have Gmail or Outlook and you need a domain route you can prove.

Why agencies copy the diagram and still fail

They share one hop-one leftover across clients. Architecture is per zone. Agency capacity is numeric. It does not merge DNS. Per-client MX, per-client map, per-client SMTP.

A complete worked story

A rewrite they called SRS

A panel labeled a Header-From change as “SRS.” DMARC died. They moved to MailerZ, kept hello@, and probed. Envelope changed. Header From was the customer again. Same word, different architecture. This page exists so the next panel gets asked which RFC they meant.

Operator brief

A longer operator brief for email forwarding architecture

Teams that bookmark Email Forwarding Architecture: Envelope, Header, SRS and Delivery Hops usually arrive after a missed invoice, a form that never notified anyone, or a migration that looked clean in one resolver. The useful brief is still boring. Name the store. Name the printed local-parts. Name the nameservers that actually answer. Publish one MailerZ MX set. Delete leftover hosts. Probe from a mailbox that is not the destination. Only then talk about email forwarding architecture as a send-as, catch-all, or comparison problem.

MailerZ remains inbound MX plus authenticated SMTP around Gmail or Outlook. Envelope SRS only. Header From, Subject, Date, Message-ID, body, and MIME stay intact. It is Mail Box portal webmail, not IMAP, not POP, and not an open relay. Unauthorized send is 550 / 550 5.7.1. Free cannot finish send-as: SMTP and API stay off. Solo is $40 per year when the domain From must travel. Starter is $8 or $80. Business is $19 or $190. Agency is $39 or $390. Unlimited is $99/month or $990/year. Confirm the live pricing page. Those numbers are ceilings, not an inbox-placement service-level agreement.

If leftover Google, Microsoft, Cloudflare routing, or registrar MX is still public, stop widening email forwarding architecture. The map you built never saw that copy. Priority numbers are an order, not load balancing. A higher preference host is idle while a leftover host still accepts mail. Save the old MX set before you delete anything. Check more than one public view because TTL lies.

Catch-all forward is not a safety feature for email forwarding architecture envelope header srs and delivery hops. Hold unknowns on everyday production. Review the store. Promote a leftover only when a real person used it. Paid forward belongs to a dated cutover. Fan-out of unknowns into two inboxes trains two spam buttons. Plus addressing on Gmail is not a custom-domain unknown policy. MailerZ will not strip plus tags on your domain the way Gmail does on @gmail.com.

Send-as is a second hop. Creating an inbound alias does not approve outbound. Catch-all does not mint a From. Copy the dashboard host, port, and TLS pair together. Set From to an identity you created. Do not paste a Gmail password into a CMS, a cron file, or a ticket. Do not mail SMTP secrets to support. Send a 550 line, a timestamp, and a Message-ID. Rotate if a secret already leaked.

Self-send from Gmail to the same Gmail account can short-circuit. That green result is why people swear email forwarding architecture works while customers vanish. Use a second provider. Put a unique subject on the probe so delivery history is searchable. If Header From was rewritten by some other forwarder, authentication stories get noisier. MailerZ does not rewrite Header From on inbound.

Agencies should keep email forwarding architecture per client zone. Separate SMTP credentials. Do not pour every client into one catch-all because the spreadsheet got long. Agency plan capacity exists so you can hold more domains and aliases. It does not replace a named list. Offboard means delete MX you own, revoke SMTP, and stop forwarding leftovers into the agency inbox.

Legal and security questions have published answers on the security, privacy, terms, DPA, and subprocessors pages. MailerZ is not SOC 2, not ISO 27001, and not HIPAA. The 14-day Free store, the 90-day Solo–Agency store, and the 180-day Unlimited store are recovery windows for hops this layer saw. They are not an archive and not legal hold. If counsel wants eDiscovery, buy eDiscovery.

Comparisons only help after the hop is honest. Cloudflare Email Routing is inbound routing. A privacy-mask product hides a destination on a provider domain. A suite hosts mailboxes, Calendar, and admin. Proton-class mailboxes encrypt a store. MailerZ is the delivery layer when you already have Gmail or Outlook and you need a domain route you can prove. Cite the other product’s documentation. Do not invent feature parity.

When Email Forwarding Architecture: Envelope, Header, SRS and Delivery Hops is closed, the next physical action is a lookup and a probe, not another tab. Start free on one domain you can break. Sign in if the zone already lives here. Review quarterly, or sooner after a nameserver move, a plugin swap, or a staff departure. That is how email forwarding architecture stays a runbook instead of an incident.

A second worked pass for email forwarding architecture: write the last change on a sticky note before you open the dashboard. Nameserver move, leftover MX, new form plugin, contractor laptop, or a registrar forwarding toggle are the usual five. MailerZ history only shows hops that reached this layer. If the sticky note says leftover MX, you do not have a email forwarding architecture mystery. You have a split. Delete the leftover. Wait for TTL. Probe again.

A third worked pass: print the public list. If you cannot print it, you are not ready for production unknowns and you are not ready for a bigger alias ceiling. Unlimited aliases as marketing will not save a missing list. Three named aliases on Free are enough to stop printing a personal Gmail on a homepage. Grow the list when a real person used a leftover, not when a harvest guessed admin@.

More working detail

Why two RFCs in one ticket saves an hour

If the complaint is “the envelope sender looks weird,” you are in RFC 5321 and SRS. If the complaint is “the From name changed,” you are in RFC 5322 and a rewrite product. Email forwarding architecture is the habit of asking which RFC before opening SPF generators. MailerZ will look “weird” on the envelope after SRS and “normal” on the header. That is correct. A registrar toy that looks “normal” on both may have stolen DKIM.

Draw five boxes on a whiteboard: MX, map, resend, store, send. Circle the leftover. Circle the self-send arrow that skips the first four. That drawing is the onboarding. Dashboards come second.

Implementation order follows the boxes. You cannot test box three while box one belongs to Google. You cannot blame box four for an empty box three. You cannot attach box five on Free and call the architecture broken.

Comparisons only after the boxes are honest. Cloudflare routing is mostly boxes one and two. A suite replaces box four with itself and often box one. Proton encrypts box four. A privacy mask avoids your domain as box one. MailerZ is boxes one through three, optional five, around a box four you already pay for.

Failure modes as architecture, not folklore

Open relay is box five without authentication. Catch-all hose is box two without a list. Header rewrite is a mutated box three. Inbox SLA is a claim about box four you cannot sell. Keep the diagram strict and the folklore dies.

One more working distinction

Where MIME and Message-ID sit in the diagram

Message-ID is a header. MailerZ does not rewrite it. That is why you can correlate hop four to hop three. MIME is the body structure. Changing it would break DKIM. Email forwarding architecture that “sanitizes” attachments on the hop is a different product with a different auth story. If you need malware scanning that mutates MIME, know that you left this architecture. Do not call the mutant SRS.

Date and Subject are also headers we leave alone. Filters that key on Subject still see the author’s subject. That is a feature of an intact hop, not a Gmail setting.

A short operating rule

How to brief an engineer in four sentences

We accept MX. We map RCPT TO to a destination. We may SRS the envelope. We do not rewrite Header From. Email forwarding architecture for a new hire is those sentences plus leftover MX is a hard stop. If they want to mutate MIME, they are designing a different service. If they want IMAP, they are in a suite. If they want open send, they get 550.

Have them run one external probe and read Authentication-Results before they touch SPF generators. The diagram sticks after one real message.

Field close

Where logs are allowed to live

Hop-three history may contain envelope recipients, timestamps, and SMTP replies. It should not become a body archive. Email forwarding architecture that stores full bodies forever is an archive product. MailerZ’s 14-day and 90-day windows are recovery, not Vault. If counsel wants more, buy more elsewhere. Do not stretch hop-three storage into eDiscovery and then claim HIPAA.

What you send to support is a timestamp, a Message-ID, a 550 line, and a public MX view. Not a password. Not a mailbox dump. Architecture includes the evidence path.

If a developer wants to log raw MIME in an app, that is their app, not this hop. Keep the forwarder boring so DKIM can live.

Last operating note

A whiteboard test for vendors

Ask them to mark which boxes they change: envelope, header, MIME, Message-ID. If they mark header or MIME and still say “SRS,” walk. Email forwarding architecture shopping is that mark-up. MailerZ marks envelope only. The rest stay the author’s. That is the buy.

How to number hops in a ticket so the diagram survives

Email forwarding architecture falls apart in chat when people say “the server” without a hop number. Write hop one as sender to MailerZ MX. Write hop two as MailerZ to the destination mailbox. Write hop three as the optional paid send-as session. If a fourth hop exists, someone else rewrote or resent the message. MailerZ history only shows hops that reached this layer. Empty history is leftover MX or a message that never used your MX, not a missing SRS feature.

Message-ID is the correlator. MailerZ does not rewrite it. Paste the same Message-ID next to the public MX screenshot and the destination original. If the destination copy has a different Message-ID, you are looking at a different message or a rewriter. If Header From changed, you are not on this architecture. Envelope Return-Path may show an SRS identity. That is hop-two SPF doing its job. Humans still read Header From.

Brief an engineer in the hop language before they open an SPF generator. Exclusive MX is hop one. Named aliases are the map on hop one. SRS is the envelope on hop two. Destination filters are after hop two. Paid SMTP is hop three and does not exist on Free. Confirm pricing. Related: email forwarding and troubleshooting.

Agencies should keep one hop diagram per client zone. Do not merge Brand A’s leftover MX into Brand B’s send-as ticket. Separate SMTP credentials. Offboard deletes MX you own. The diagram is the product you can hand to the next operator without folklore.

FAQ

What is the safest way to handle email forwarding architecture?

Treat forwarding as a second SMTP hop: exclusive MX, named alias map, SRS on the envelope, Header From intact, destination store in Gmail or Outlook. Name the dead hop. Do not rewrite the visible From. Probe from another mailbox.

Does this require a new mailbox?

No. MailerZ is Mail Box portal webmail (Inbox, Sent, New email). It is not IMAP or POP. Gmail or Outlook remains the store unless you separately buy a hosted mailbox product.

Will it work with Gmail or Outlook?

Yes for inbound when the destination is a verified mailbox. Branded replies need paid send-as plus Gmail Send mail as or a manual Outlook SMTP identity. Free has no send-as.

What DNS records are involved?

A verification TXT, one MailerZ MX set on the authoritative nameservers, leftover host MX removed, and SPF, DKIM, and DMARC if you also send as the domain.

What should I test before production?

Send a uniquely titled message from an unrelated provider into each named alias. Confirm Header From and delivery history. Do not email yourself from the same Gmail account.

Key takeaways

• Second SMTP hop.
• SRS = envelope.
• Header stays.
• Name hops.
• Exclusive MX.
• Map ≠ mailbox.
• Hop five optional paid.
• No open relay.

Conclusion and next action

Email forwarding architecture is an honest envelope, an intact header, and hops you can name. MailerZ is built on that split. Cut leftover MX so hop one is real.

Start free. Sign in if the diagram is clean and public MX still shows Google.

Review quarterly, or sooner if Gmail, Workspace, or MailerZ scope changes. Author: MailerZ editorial, Secuno LLC.