Email forwarding rejection diagnosis is hop ownership, not a feeling. Either MailerZ never accepted the message, MailerZ accepted and Gmail or Outlook later refused, or MailerZ refused the recipient at the door. Empty history is leftover MX or a name that never arrived. A 250 followed by a destination 5xx is not an MX bug. Copy the SMTP line before you toggle DNS.
Quick answer for email forwarding rejection diagnosis
IETF RFC 5321 — Simple Mail Transfer Protocol is two conversations. The sender talks to your MX. The forwarder talks to the destination. A customer bounce can come from either hop. Treating every bounce as “MailerZ is down” or every empty inbox as “Gmail ate it” is how you spend a day on the wrong object.
Open hop history for the unique subject. If there is no row, the message did not reach MailerZ. Typical causes: leftover Google or registrar MX, wrong panel, or the sender never left their own queue. If there is a row with 250 at accept and a later destination 421, 450, or 550, the forwarder did its job and the store refused. If accept is 550, MailerZ refused the recipient: unknown on a hold or reject path, unauthorized, or unhosted. Free holds unknown. It does not invent a named alias you forgot to create.
Recovery storage is 14 days on Free and 90 days on paid. It is a failed-hop window, not IMAP and not a seven-year archive. If the old host accepted the message, MailerZ has nothing to show. That empty row is the proof, not a missing product feature. Screenshot the empty search with the unique subject in the query. That screenshot is how you prove you looked. Support should not have to guess whether you searched last week’s invoice title or today’s nonce.
A destination 250 with the message in spam is still not rejection. Rejection is an SMTP refuse. Filters are a later folder. Founders merge those words and then “fix” DKIM. DKIM may already have passed. The folder is Gmail. MailerZ does not sell Primary. Say reject only when the hop said 4xx or 5xx, or when hop one never happened.
MailerZ Free is one domain, three aliases, 14-day store, one seat, send-as disabled, SMTP and API disabled. Solo is $40 per year. Starter is $8 or $80. Business is $19 or $190. Agency is $39 or $390. Unlimited is $99/month or $990/year. Confirm pricing. A longer store helps when MailerZ accepted and the destination later failed. It does not create hops that never happened.
Related pages: evidence before support, leftover MX, why storing a failed message matters, troubleshooting. This page is the owner test.
The user problem and the decision criteria
Founders hear “I sent it” and open Gmail. Nothing. They republish Workspace MX, rotate DKIM, and upgrade the plan. The invoice is sitting on the leftover host, or Gmail returned 550 after MailerZ already accepted, or billing@ was never created. Three owners. One panic. Email forwarding rejection diagnosis exists so you name one owner before you touch the zone.
| History | Owner | Next action |
|---|---|---|
| No hop row after a unique probe | Never reached MailerZ | Public MX. Leftovers. Wrong panel. Sender queue. |
| Accept 550 / unknown | Forwarder recipient policy | Create the named alias. Check hold on Free. |
| Accept 250, destination 4xx | Destination deferral | Wait and watch. Do not toggle MX. |
| Accept 250, destination 5xx | Destination permanent | Read the enhanced status. Fix Gmail or the address. |
| Self-send, no useful history | Invalid test | Third mailbox. See self-send article. |
| Customer bounce, you never probed | Unknown | Reproduce with a unique subject first. |
Agencies paste the hop line into the ticket, not “it bounced.” A 421 from Gmail and a 550 from MailerZ are different runbooks. Mixing them is how leftover MX returns on Friday.
Do not diagnose send-as AUTH in this ticket. AUTH failed means the client never submitted outbound. That is SMTP authentication failed. Inbound rejection is a different SMTP conversation.
Technical mail flow for the two hops
Hop one: the sender looks up MX, connects, offers MAIL FROM and RCPT TO. MailerZ accepts a named alias, stores required content, returns 250, and queues the forward. Envelope MAIL FROM is rewritten with SRS. Header From stays the original sender. See email forwarding.
Hop two: MailerZ connects to Gmail or Outlook as a client. That conversation has its own 250, 4xx, or 5xx. History should show that reply. If hop two is 550 mailbox unavailable, the destination rejected. Republishing MX will not make Gmail accept a disabled user.
Leftover MX splits hop one. Some senders still connect to Google. Those messages never create a MailerZ row. Customers are not lying. You are looking in the wrong store. Delete leftovers. Leftover MX tool.
Unknown recipients on Free are held. That is not a destination reject. The message reached MailerZ and waited. Check hold before you tell the customer Gmail failed. Paid catch-all forward is a later choice after an abuse audit, not a substitute for creating printed names.
IETF RFC 1035 — Domain names does not reject mail. Bad DNS can prevent hop one. That still looks like empty history. Confirm exclusive MX on two public resolvers before you read Gmail as the villain.
The evidence order
Unique subject from a mailbox you do not own
Date and a nonce in the subject. Self-send from Gmail can short-circuit. Self-send tests.
Public MX on two resolvers
Exclusive MailerZ hosts. Any Google, Microsoft, registrar, or null MX means you are not diagnosing the forwarder yet.
Hop history for that subject
Empty, accept 550, or accept 250 plus destination status. Copy the line verbatim. Enhanced codes matter: 5.7.1 is not 5.1.1.
Hold queue if the local-part was unknown
Free holds. Creating the alias later can still matter inside the store window. Do not restore Workspace MX to “find” a held message.
Customer bounce only after you reproduced
Their screenshot is useful. Your unique probe is the ticket. Support cannot work “sometimes.”
Write UTC timestamps. A destination 421 at 14:02 and a 250 at 14:40 is deferral, not a product outage. See the later 421 article when you need that code named. This page is the owner split.
Enhanced status text is part of the evidence. “Mailbox unavailable” and “policy violation” are different owners inside hop two. Copy both the numeric code and the English. Do not paraphrase into “Gmail said no.” A future you will not remember which no.
If two aliases fail and one works, you do not have a global MailerZ outage. You have a per-recipient map. Diagnose the failing local-parts. If every alias is empty history, you have leftover MX or a dead sender. If every alias is destination 550, you have a destination account problem. Those three patterns save an hour.
Phone screenshots of a red banner are not hop evidence. Ask for the raw bounce or reproduce. Consumers forward a banner. Operators forward a status line. Train the team once.
Catch-all hold fills with guessed names. That is not destination rejection. Opening hold and seeing noise does not mean hello@ failed. Filter hold by the unique subject you sent. Mixed hold and named-alias tickets are how people restore Google MX for spam they asked for.
International senders and IPv6-only MTAs still must hit your exclusive MX. If a region “never arrives,” compare that region’s public lookup to 8.8.8.8. Sticky resolvers exist. Dual MX is still wrong. See MX propagation for the wait, leftover MX for the second hostname.
Step-by-step: prove who rejected
Confirm the alias exists
Printed names must be named rows. Free has three aliases. Guessed catch-all is hold, not Gmail.
Confirm exclusive MX
MX lookup from two resolvers. Delete leftovers in the same hour if they still show.
Send the unique probe
Outlook.com, a phone carrier, or a colleague. Not the destination Gmail talking to itself.
Classify history
Empty: hop one. Accept 550: MailerZ recipient. 250 plus destination 4xx/5xx: hop two. Write the owner in the ticket title.
Fix only that owner
Empty means DNS or sender. 550 accept means create the alias or read hold. Destination 5xx means the store. Do not rotate SPF for an empty hop.
Repeat one probe after the fix
Same uniqueness rule. If the owner was leftover MX, history should appear. If the owner was Gmail 550, history will still show 550 until Gmail changes.
If you must contact support, attach the hop line, the two MX lookups, and the unique subject. See evidence to collect. A toast from Outlook is not evidence.
Failure modes that look like “they rejected it”
Leftover MX. Proof: no hop, public MX still lists Google. Fix: delete. The old host may have the copy.
Wrong panel. Proof: public NS ≠ the account you edited. Fix: authoritative host. NS vs registrar.
Missing alias. Proof: accept 550 or hold. Fix: create the name. Do not dual-publish MX.
Destination full or disabled. Proof: hop two 5xx mailbox. Fix: Gmail or Outlook admin. MailerZ already accepted.
Temporary greylist. Proof: hop two 4xx then later 250. Fix: wait. Do not toggle MX. The 421 article covers that class.
Self-send. Proof: Gmail never left Google. Fix: third mailbox.
Customer sent to a typo. Proof: history for a different local-part or empty if leftovers ate it. Fix: the printed address list.
Store window expired. Proof: you look for a hop from three weeks ago on Free. Fix: paid 90-day store next time. The message is still not in Gmail if hop two failed then.
Spam folder, not a reject. Proof: hop two 250, message in Promotions or spam. Fix: that is filters, not rejection. No inbox SLA. Green checks are not Primary.
From rewrite at another hop. Proof: Header From is not the author. Fix: leave that product. MailerZ does not rewrite From. That is a different ticket from rejection.
MailerZ workflow and the product boundary
MailerZ records hops it took. It does not log Google’s leftover MX. It is not Workspace, not IMAP, not webmail, not an open relay, not SOC 2. Security. Docs. Unauthorized outbound still 550. That is send-as, not inbound diagnosis.
Seats operate the dashboard. They do not add hop rows. Agency at $39 or $390 still diagnoses one unique subject at a time.
Header From stays intact on forwards. Envelope SRS only. A destination 5xx after an honest hop is still a destination 5xx. Do not rewrite From to “help” a reject. That breaks DKIM. See the DKIM and From-rewrite articles already on the site. Do not edit those files.
Compare routing-only tools if you are leaving them: Cloudflare Email Routing, ImprovMX. Judge whether they store destination SMTP. This page assumes you can read a hop.
Failed-hop store is 14 or 90 days. Use it. If the window is empty and MX is exclusive, the sender never arrived or you searched the wrong subject.
Cost of a named hop versus a day of toggles
The probe is free. The screenshot is free. Dual MX for a day is expensive. Solo at $40 per year buys 90-day store so last week’s destination 550 is still readable. Starter, Business, and Agency scale domains and send ceilings. Annual paid cards except Solo include two months free versus monthly. Confirm pricing.
Do not buy Agency to get a clearer bounce. The SMTP line is the same class of object on every plan that stores the hop. Do not buy Google Workspace — product overview to diagnose a leftover MX split. The suite will accept mail you thought was missing.
Staff time is the line item. One owner, one unique subject, one hop line. Slack “Gmail is broken” without history is how MX oscillates.
Tools: tools hub, leftover MX, MX lookup. Enough for hop one. Hop two lives in history.
If legal needs evidence, export the hop line and the .eml you still have. MailerZ is not a legal archive. Say that before someone treats 14 days as discovery.
A founder who escalates to Agency during an empty-hop ticket is buying domain ceiling, not a missing Google leftover. The hop line does not get clearer at $39 or $390. Exclusive MX and a third mailbox do. Write the plan card after the owner is named, not instead of naming it.
Timeboxes help. Fifteen minutes for MX lookups and one probe. If history is empty, leftover MX is the default until two resolvers disagree. If history shows destination 550, stop the DNS window and open the Gmail admin. Oscillating between those two for an hour is how Friday becomes Monday.
Shared inboxes at the destination do not change hop ownership. If sales@ maps to two Gmail accounts and only one is disabled, hop two may 550 on one attempt and 250 on another depending on how the destination is written. Read the destination field in the dashboard. Do not assume “the team inbox” is one SMTP target.
Website forms that send to hello@ are inbound to MailerZ only after a stranger’s MTA looks up your MX. A form that posts to Gmail’s HTTP API never creates a MailerZ hop. People call that a reject. It is a different transport. Ask how the form sends before you read history.
Cron and monitoring alerts that SMTP to MailerZ are outbound send-as, not inbound forwarding. A 550 5.7.1 there is unauthorized From. Do not open this inbound checklist for that. Keep the two SMTP conversations in two tickets even when the brand address looks the same.
Related diagnosis pages already on the site: 450 vs 451 vs 452, DNS looks correct, MX troubleshooting. Use them after this owner split. They do not replace a unique subject.
Write the customer sentence: “We accepted the message at HH:MM and Gmail returned CODE,” or “Your message never reached our MX; public DNS still shows the old host.” Those two sentences end most arguments. “We’re looking into email” extends them.
Field notes for operators
Put the unique subject in the ticket title. “Bounce” is not a title. “2026-09-09-billing-probe-7f3 empty hop leftover Google MX” is a title. The next person can finish without a call.
If three customers fail and your probe succeeds, ask those customers for the destination they typed. Typos to a hold or to leftover Google explain the split. Do not dual-publish because three people mistyped.
Registrar “email connected” badges are not hop evidence. Pretty panels lie. Two public resolvers and a hop row do not. Run MX lookup even when the badge is green.
When hop two is 5.7.1 after a From rewrite at another vendor, you have two problems. This page owns the reject. The From-rewrite pages already on disk own the identity. Do not edit those files. Do not merge the tickets until both owners are named.
Night-shift rollback during an empty-hop ticket is usually leftover MX panic. If public MX already shows exclusive MailerZ and history is empty, the sender never arrived or the subject is wrong. Restoring Google MX then guarantees a split. Wait for the customer’s raw bounce before you roll back. Rollback is a different page.
Train sales not to promise “we will find the message.” You will find a hop, a hold, or a leftover host. You will not find a seven-year archive. That sentence belongs on the first call. If a prospect asks for SOC 2 because of one bounce, point them at security. The hop line is still the diagnosis. A badge you do not have will not appear because leftover MX hid an invoice.
FAQ
How do you prove email forwarding rejection diagnosis?
Send a uniquely titled message from a mailbox you do not own. Open MailerZ hop history. Empty history means the message never reached the forwarder. A 250 then a destination 4xx or 5xx means Gmail or Outlook refused. A 550 at accept means MailerZ refused the recipient. Copy the SMTP line before you change MX.
Does this require a new mailbox?
No. Diagnosis is hop evidence. Destinations stay Gmail or Outlook. MailerZ is not IMAP. Buying a suite seat does not create a missing hop row.
Will it work with Gmail or Outlook?
Yes as destinations after exclusive MX. Those providers return the destination SMTP you will copy. Self-send from Gmail to Gmail can hide both hops. Probe from another provider.
What DNS records are involved?
Exclusive MailerZ MX so the probe actually hits the forwarder. Leftover Google MX sends the message to a host that will never appear in MailerZ history. Verification TXT should already match. SPF does not explain an empty hop.
What should I test before production?
Named alias created, leftovers gone, unique inbound from a third mailbox, hop row copied. If history is empty, stop blaming Gmail. If history shows destination 5xx, stop republishing MX.
Key takeaways
- Empty history means hop one never hit MailerZ.
- Accept 250 plus destination 5xx is Gmail or Outlook, not MX.
- Accept 550 is MailerZ recipient policy. Check aliases and hold.
- Leftover MX is the usual empty-history cause.
- Copy the SMTP line before you change DNS.
- Self-send is not a diagnosis.
- Spam folder after 250 is not a reject.
- Free store is 14 days. Paid is 90.
- Do not rotate SPF or DKIM for an empty hop.
- Do not rewrite From to fix a destination 550.
- MailerZ is not IMAP, not a suite, and not SOC 2.
- One unique subject per ticket.
- Two aliases failing and one working is a map problem, not a global outage.
- A form that posts to Gmail’s API never creates a MailerZ hop.
- Outbound 550 5.7.1 is send-as, not inbound rejection.
Conclusion and next action
Email forwarding rejection diagnosis names the hop. Empty, accept-fail, or destination-fail. Everything else is a different ticket.
Next action: exclusive MX, named alias, unique probe from another mailbox, copy history. If empty, delete leftovers or fix NS. If accept 550, create the alias or read hold. If destination 5xx, take that line to Gmail or Outlook. Do not republish Google MX to “be safe.”
Keep the hop line next to the alias list. The next bounce should take five minutes. That is the only reason this order exists. If the line is missing, you guessed. Guessing is how leftover MX returns. Write the line even when the news is “empty hop.” Empty is an answer. Paste the two public MX lookups under that line so leftover hosts cannot hide in a verbal report.
Ready to read hops instead of guessing
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Review quarterly, or sooner if hop history labels change. Author: MailerZ editorial, Secuno LLC.