r/emaildeliverability

Adding any domain to Postmaster Tools fails with a generic "Adding domain unsuccessful" toast.

No 4xx or 5xx to chase; the add call is a POST to `/batchexecute` which returns HTTP 200 with the error buried in the response body:

```rpcid MFo2Gb [5, null, [["type.googleapis.com/apps.postmaster.postbox.PostboxErrorInfo",[1]]]] 5 is gRPC NOT_FOUND. ```

"postbox" appears to be the internal service name.

Frontend build boq_gmail-postmaster-ui_20260816.04.

Ruled out:

- SPF/DKIM/MX all valid,
- site-verification ownership confirmed in Search Console, super admin,
- additional-services access On for all operating units, browsers, incognito and normal profiles. - - Fails identically for a domain I don't own, so it's account-scoped rather than domain-scoped.

Anyone else seeing this, or know what that error enum maps to?

I run cold email for a B2B agency (targets are agencies/SaaS/automation shops — so mostly Google Workspace inboxes). I've burned two full batches of domains the exact same way and can't isolate the root cause. Would love a second set of eyes. (Disclosure, this is written by Claude; I had it write the post to collect all the data, tests, and progress I made with figuring out deliverability so I don't miss anything, i want to make a genuine service that helps businesses get more clients, but dealing with email deliverability is so disheartening, especially if you don't have a lot of capital, so i made this post detailing all ive tested and symptoms with the hopes of diagnosing the problem and have mailboxes survive atleast the first 2 weeks of sending)

Setup

• Smartlead, Google Workspace mailboxes, domains + mailboxes from InboxKit, 5 mailboxes/domain
• De-clustered domain names (not obvious cousin variants). All redirect to my real company site → Calendly (temporary while i make a vsl and get more proof of work with clients)
• Copy: plain text, name-only signature, no links/images in email 1, spintax + AI icebreakers, tracking off, randomized sends, 3-min gaps
• Warmup: Batch 1 = fresh, 2 weeks Smartlead warmup. Batch 2 = pre-warmed 4 weeks. Warmup left on. Ramp 5→10/day, in 5 increments every week
• Lists: Sales Nav → AnyMailFinder → Bouncer-verified, Google inboxes only. Bounce rate 0.4–1.5%

What happens (identical both batches)

• Domains land on SURBL (ABUSE) within week 1 (with the exception of 1 domain per batch, those domains always stay healthy while the others die)
• Everything looks fine for ~2 weeks: 15% reply rate, 60% positive, warmup health 90–100%
• Then warmup health collapses almost in 1 day to 80% then goes down day by day. Inbox placement test to fresh seeds: SURBL-listed domains hit 0/10 inbox, 10/10 spam. Dead

What I've tested / ruled out

• SPF/DKIM/DMARC all pass, mail-tester 9–10/10
• Per-domain SURBL check maps 1:1 — listed domains = 100% spam/dead; the one un-listed domain in each batch survives
• Redirect target (my own domain) is clean on SURBL, so they're not inheriting the listing from it
• Bounce rates are low, so lists aren't full of dead addresses
• Same copy AND same lists went to the survivor too
• Warmup health score is worthless as a signal if below 98%, one domain read 96% warmup while landing 100% spam on real seeds
• When the first batch died, I tried getting 4-week warmed mailboxes instead of 2 yet it's the same story

The part I can't explain — mirror-image audience split

• My aged brand domain (sent the exact same lists, same volume, never burned): inbox on Workspace, spam on consumer Gmail
• The fresh survivor: inbox on Google Workspace, spam on normal Gmail accounts (which isn't a big deal because all my lists consist of Google Workspace)

My thoughts

1. Pristine spam traps in the "verified" lists (Bouncer/AnyMailFinder can't catch live traps; pattern-guessed emails are risky) — whichever domain's slice hits a trap gets SURBL-listed and dies first
2. Age/legitimacy is the real survival factor; fresh domains never earn Workspace trust through warmup alone

Questions
Why do fresh domains keep getting SURBL-AB listed within a week even off verified lists? I've read that being blacklisted by SURBL is only the symptom of deliverability, not the problem, so what could be the main issue causing it? why do all my domains die with the exception of 1 every time? if its spam traps that are causing this, what can you do to avoid them?

So a bit context, I'm a freelance copywriter and I have worked with a few clients and I used to handle all the writing stuff, yk emails and email sequences

Now I'm deciding to take a step further and get more into the back ends of email ykwim

Yk ensuring emails landing in primary and not promo or spam, this was I can like give them a package deal of like

I write the emails, and ensure they land in primary as well

Also if anyone doing what I'm thinking of doing, let's connect guys!

As the title says, for weeks I have been running a few mailboxes on a good-performing campaign, getting positive replies, booking calls, same list-building steps, bounce rates around 1.5-0.5%, and then out of nowhere, in a few hours today, all the mailboxes on the campaign tank in warm up reputation, not my by much (from 100% for weeks to 89% in a few hours).

That might look like a good sign because of how small the drop is, but from my experience it's usually the beginning of the end for the fleet. What I want to find out is what could have caused this. Have you guys run into similar situations?

I use InboxKit for domains and mailboxes with their InfraGuard (which coincidentally I bought today, which is the same day the mailboxes tanked, but idk how it would be responsible), Smartlead for sending, Sales Nav, and Bouncer for leads and email validation

Hey everyone,

I'm currently setting up **MailWizz** for a new cold email campaign and I want to make sure I’m not missing anything critical before I go live.

I’m trying to keep the setup relatively **pocket-friendly**, but I know that cutting too many corners usually leads to the spam folder. I'd love to hear from anyone who has a solid self-hosted workflow.

Specifically, I’m looking for suggestions on:

* **Hosting:** Where are you guys running MailWizz? I was thinking of a basic VPS like Vultr or DigitalOcean—is that enough, or is there a better budget-friendly pick? * **SMTPs:** Which providers are actually playing nice with cold outreach lately? * **Essential "Extras":** What else should I have in my stack for list cleaning or warm-up? * **The "Gotchas":** Any major pitfalls or settings I should double-check while the campaign is running to keep my deliverability from tanking?

If you’ve been through the trial and error of setting this up recently, I’d really appreciate your insights!

Cheers.

I'm troubleshooting a Microsoft-specific deliverability issue with my email addresses

Emails are landing in Gmail inboxes (with 100% deliverability)

But Microsoft 365/Outlook is consistently sending them to Junk even though SPF, DKIM, and DMARC all pass (it is 0% develiverability in M365/Outlook mailboxes)

Microsoft Deliverability Support asked me for 3-4 recipient-side .eml samples from M365 mailboxes where the message landed in Junk.

If you have a Microsoft 365 mailbox and can help:

• DM me an email address you're comfortable using
• I'll send one harmless business-style email
• If it lands in Junk, please download it as .eml and send it back to me

I'll only use the file for my open Microsoft support case.

Please DM me rather than posting your email publicly. Thanks!

Recently, a client forwarded me a screenshot of one of our email campaigns landing in promotions. Had another client complain of landing in spam.

I checked the Google Postmaster Tools, sure enough, our spam rate had been climbing for the past 3 days.

We would have caught them within a few days. But I just realized how reactive our deliverability monitoring had become.

Four days. Four sends. And we had no idea until it came to our attention by chance.

We had the data. Nothing was broken. We had Postmaster Tools, campaign reporting, bounce data, complaints, etc. But nobody was checking everything every morning. But we have to be real, a dozen other things are splitting our time.

That got me wondering how other teams handle this.

I'm interested in how agencies or teams managing multiple ecommerce brands handle this.

Do you have someone actively monitoring sender reputation and spam rates every day? Or have you set up alerts when something starts moving in the wrong direction?

If you're running cold email through SuperSend, check your inbox. I just got an email from Kurtis Tryber at SuperSend with some important news.

The short version: SuperESP, the dedicated cold email sending infrastructure SuperSend used, got mass-blacklisted by Spamhaus over the last 72 hours (as of yesterday). SuperSend tried to fix it and couldn't find a reliable path forward, so they're shutting SuperESP down entirely and closing any account that depended on it.

Key points from the notice:

• SuperSend as a company/platform is NOT shutting down. This is specifically about the SuperESP sending infrastructure.
• If your account used SuperESP, it's being closed. Your most recent invoice gets refunded in full.
• No more outbound mail will go through SuperESP after the date of notice.
• You have 30 days to log into app.supersend.io and export your contacts, campaigns, and history before the account and data are deleted.
• If you were still in warmup and hadn't sent production email yet, you still get the full refund even though you got zero value out of it.

If this affects you, you might not want to wait around. Log in now and export everything you need. I wouldn't assume "30 days" is a hard guarantee that nothing goes sideways sooner.

Posting this in case anyone else got this email and is now scrambling to figure out where to move their cold email sending. Curious what people are migrating to or if you have any additional context on this you can share.

When you see emails landing in spam, what's the reason or checklist u go through to ensure why are those emails landing in the spam tab?