How to improve email deliverability

To improve email deliverability, authenticate your sending domain with SPF, DKIM and DMARC, and verify your list before every campaign so invalid addresses never bounce. Warm up new domains and mailboxes and send at steady volumes. Write short, relevant messages with an easy way to opt out. Then monitor bounces, spam complaints and inbox placement so you catch and fix problems early.

What email deliverability depends on

Email deliverability is whether your message reaches the inbox rather than the spam folder or nowhere at all. For a fuller definition, see what is email deliverability.

Mailbox providers such as Gmail and Microsoft decide placement from a handful of signals:

Whether your domain proves it sent the message (authentication).
How your sending reputation looks over time.
How many of your messages bounce.
How recipients react: replying, deleting, ignoring or marking as spam.

Content matters, but usually less than reputation and list quality. Most fixes therefore fall into four groups: authentication, list hygiene, sending behaviour and content. Work through them in that order. A well-written email from an unauthenticated domain to a stale list will still struggle.

Authenticate your sending domain

Set up three DNS records on every domain you send from:

SPF lists the servers allowed to send mail for your domain.
DKIM adds a cryptographic signature showing the message came from your domain and was not altered.
DMARC tells receivers what to do when SPF or DKIM fail, and sends you reports. Start with a monitoring policy (p=none), read the reports, then move to quarantine or reject once your legitimate mail passes.

Gmail and Yahoo require bulk senders to authenticate with SPF, DKIM and DMARC and to support easy unsubscribes, so this step is no longer optional. Check alignment as well: the domain in your From address should match the domain that SPF or DKIM authenticates.

Many teams send cold outreach from a separate domain so that a reputation problem with prospecting mail does not affect invoices, support and product email on the main domain. A secondary domain needs its own SPF, DKIM and DMARC records.

Clean your list before you send

Bounces are one of the fastest ways to damage sender reputation. A hard bounce tells the provider you are mailing addresses that do not exist, which is what senders of bought lists do. Keep your bounce rate low (what is a good email bounce rate covers typical benchmarks) by verifying addresses before each campaign, not only when you first collect them. People change jobs, and an address that worked last quarter may not work today.

Useful verification goes beyond syntax. It checks DNS and MX records, asks the mail server whether the mailbox exists, and sorts results into clear groups:

Verified or valid: send.
Catch-all: the domain accepts every address, so the specific mailbox cannot be confirmed. Send at lower volume or in a separate segment. See what is a catch-all email.
Unknown: the server gave no clear answer. Treat it as unconfirmed.
Invalid: remove it.

Also remove shared role addresses such as info@ and sales@ from cold campaigns, suppress anyone who has unsubscribed or complained, and avoid lists you cannot trace to a source.

This is the step where a data tool can help. Leadsets email verification runs a waterfall (syntax, DNS and MX, a mailbox-level check, then a second verifier for uncertain or catch-all results) and labels each address verified, catch-all, unknown or invalid with a confidence score. Uncertain results are never rounded up to valid, and invalid emails are never served as contact emails. Other verifiers do similar work; what matters most is that you act on the labels rather than sending to everything.

Warm up and pace your sending

New domains and mailboxes have no reputation, and a sudden burst of messages looks like abuse. Start with small daily volumes to people likely to engage, raise volume gradually over several weeks, and keep it steady rather than spiky. Spread sending across several mailboxes instead of pushing one inbox hard. After a long pause, ramp back up rather than resuming at full volume.

Write emails people want to receive

Engagement feeds reputation, so relevance is a deliverability tactic. Send to a tight audience that matches your ideal customer, keep messages short and mostly plain text, give a specific reason for reaching out, and avoid heavy images, link shorteners and lots of links. Make it easy to opt out. A clear unsubscribe line costs you a few recipients but prevents spam complaints, which do far more damage.

The guide on how to write a cold email covers structure and tone. Cold outreach also has to follow the rules where your recipients are; see is cold email legal.

Monitor and fix problems

Track bounce rate, spam complaint rate, reply rate and inbox placement for each mailbox and each domain. Google Postmaster Tools shows domain reputation and spam rate for mail sent to Gmail users, and Microsoft offers Smart Network Data Services (SNDS) for its network.

When deliverability drops, work through this sequence:

Pause the affected campaign and mailbox.
Confirm SPF, DKIM and DMARC still pass and align.
Re-verify the list and remove invalid and unknown addresses.
Check whether your domain or sending IP appears on public blocklists.
Restart at lower volume to your most engaged contacts, then ramp back up.

Reputation damage usually recovers with time and clean sending. There is rarely a single setting that fixes it.

A worked example

Maya Chen, VP Revenue Operations at Northwind Analytics (northwind.co), notices reply rates falling and bounces rising on an outbound campaign. Two causes turn up: DMARC was never configured on the secondary sending domain, and the list was last verified months ago.

She adds a DMARC record with a monitoring policy and re-verifies the whole list. She removes the invalid addresses, holds the unknown ones, moves catch-all addresses into a separate low-volume sequence, and restarts each mailbox at reduced volume before ramping up again.

If Maya works in Claude with Leadsets connected, the free, open-source Pre-send campaign check skill runs a final verification on a loaded campaign and pauses risky contacts before launch, and the Catch-all segmenter skill separates catch-all domains so they can be warmed at lower volume rather than dropped.

Questions and answers

Why are my emails going to spam?

The most common causes are missing or misaligned SPF, DKIM and DMARC records, a high bounce rate from unverified lists, sudden spikes in sending volume and spam complaints from recipients who did not expect the email. Content issues such as many links or heavy images can add to the problem but are rarely the only cause.

How do I fix poor email deliverability?

Pause the affected campaign, confirm your authentication records pass, re-verify the list and remove invalid addresses, and check blocklists. Then restart at lower volume to engaged contacts and increase gradually while watching bounce and complaint rates.

Does email verification improve deliverability?

Yes. Verification removes addresses that would hard bounce, and a low bounce rate protects sender reputation with mailbox providers. It works best when run shortly before each send, because addresses go stale as people change jobs.

Should I send to catch-all email addresses?

Catch-all domains accept every address, so the specific mailbox cannot be confirmed in advance. A common approach is to send to them in a separate segment at lower volume and drop any that bounce, rather than mixing them with verified addresses.

How long does it take to warm up a new sending domain?

Warm-up usually takes several weeks of small, steady volumes that increase gradually. Sending to people likely to engage during this period helps the domain build a positive reputation faster.

What is the difference between delivery rate and deliverability?

Delivery rate measures how many emails were accepted by the receiving server rather than bouncing. Deliverability is narrower and harder to see: it is whether accepted emails land in the inbox instead of the spam folder.

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