# Why your transactional email goes to spam

_By Tayyab Mughal, Founder & AI Chief · 20 August 2026 · 8 min read_

> Password resets and receipts land in spam for different reasons than marketing mail. Reputation is shared across your domain, warm-up cannot be skipped, and the fixes are mostly not about content.

People assume transactional mail is exempt from filtering because it was requested. Mailbox providers do not know that, and mostly do not care.

## The wrong mental model

Most people debugging this start with the message: the subject line, the wording, the number of links. That is where spam advice has always pointed, and for transactional mail it is usually the least productive place to look.

Mailbox providers are making a judgement about the sender first. Content matters at the margin, once reputation has already put you near a threshold.

## Reputation is shared, and your marketing team is spending it

Your domain has one reputation. If your marketing platform sends a campaign to a stale purchased list on Monday, your password resets are landing in spam on Tuesday — from an entirely different system, with perfect authentication.

This is the strongest argument for subdomain separation. Send transactional mail from a subdomain that only ever carries transactional mail, and marketing from another. A bad campaign then damages a reputation you can afford to lose.

| Subdomain | Carries | Why |
| --- | --- | --- |
| mail.example.com | Password resets, receipts, alerts | Protected from campaign damage |
| news.example.com | Newsletters, campaigns, product updates | Where complaint risk lives |
| example.com | Person-to-person mail only | Keep the root clean |

## A new IP or domain has no reputation, which is not the same as good reputation

Sending fifty thousand messages on day one from a brand-new sending identity looks exactly like a spammer who just bought infrastructure, because it is what spammers do. Providers throttle or drop it.

Warm-up means increasing volume gradually so a pattern establishes. Two weeks is fast; six is common. There is no way to buy your way past it, and this is the constraint founders consistently underestimate when planning a launch.

> If you are launching in six weeks, start sending real mail on your launch identity this week. Reputation is the one input that money and engineering cannot accelerate.

## The two numbers that decide it

Complaint rate and bounce rate. Complaints below 0.10% are healthy; 0.30% is where major providers stop accepting your mail. Hard bounces above around 5% signal you are sending to a list you do not maintain.

Both are lagging indicators of list hygiene, which is why they cannot be fixed the week you notice them.

## Things that are genuinely content problems

- A single tracked link wrapping the whole message, on a shortener domain shared with other senders.
- An image-only email with almost no text — a long-standing spam signature.
- Mismatched display name and From address, which reads as impersonation.
- A reply-to on a domain unrelated to the sending domain.
- No plain-text alternative on an HTML message.

## Debug in this order

Check authentication first, because it is binary and cheap to verify. Then reputation, because it explains most of the rest. Then content, which is where most people incorrectly start.

- Confirm SPF, DKIM and DMARC pass and align — read the raw headers of a message you actually received, not a testing tool's summary.
- Check your complaint and bounce rates against 0.10% and 5%.
- Check whether you are on a blocklist, and whether your IP is shared with someone who put you there.
- Check whether marketing and transactional mail share a domain.
- Only then look at the message itself.

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_Tags: Deliverability, Reputation_