Cold Emails Going to Spam? How to Fix It

Few things are more frustrating in outbound than writing a good email and having it land in junk. Replies dry up, and it is not obvious whether the problem is the copy, the list or something technical. In our experience, cold emails going to spam almost always trace back to a small set of causes: authentication, sender reputation, sending volume, list quality and, less often, content. This guide shows how to diagnose each one in order, with commands you can run today, and how multi-domain warming helps restore and protect inbox placement.

Cold emails going to spam? How mailbox providers decide

Gmail, Outlook and Yahoo weigh many signals, but they fall into four groups:

• Authentication: can the provider confirm that your domain authorised this message?
• Reputation: how have messages from this domain, mailbox and IP behaved in the past?
• Engagement: do recipients reply, read and move messages out of spam, or delete and report them?
• Content: do the message, links and formatting look like typical spam?

Fix them in that order. Content tweaks rarely help if authentication is broken or reputation is damaged.

Step 1: Check authentication first

Google's email sender guidelines require authentication for all senders, with stricter rules for bulk senders, and Yahoo's sender best practices say much the same. Missing or broken records are the most common technical cause we find.

Worked example: checking your DNS records

Run these commands against each sending domain (replace getacme.co with yours, and google with your DKIM selector):

# SPF: there should be exactly one record starting with v=spf1
dig +short TXT getacme.co

# DKIM: the selector depends on your provider (for example "google" on Google Workspace)
dig +short TXT google._domainkey.getacme.co

# DMARC
dig +short TXT _dmarc.getacme.co

A healthy result looks something like this:

"v=spf1 include:_spf.google.com ~all"
"v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA..."
"v=DMARC1; p=none; rua=mailto:[email protected]"

Common problems include two SPF records on one domain, an SPF record that does not include your sending tool, a DKIM key that was published but never switched on, and no DMARC record at all.

Worked example: reading the message headers

Send a test email to a Gmail address you control, open it, choose "Show original", and look for the Authentication-Results header:

Authentication-Results: mx.google.com;
       dkim=pass [email protected] header.s=google;
       spf=pass (google.com: domain of [email protected] designates 209.85.220.41 as permitted sender) [email protected];
       dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=getacme.co

You want pass for SPF, DKIM and DMARC, with the domains aligned to your From address. If any of them fail, fix that before looking at anything else.

Step 2: Check sender reputation

If authentication passes but cold emails are still going to spam, reputation is the next suspect.

• Set up Google Postmaster Tools for each sending domain. Once you send enough volume to Gmail users, it reports domain reputation and spam rate.
• Check each sending domain against the major blocklists.
• Look at recent history: did placement drop after a volume increase, a new list, or a new sending tool?

Reputation attaches to the domain and the mailbox. If you have been sending cold email from your main company domain, this is where the damage shows up, and it can affect your everyday business email too.

Step 3: Check volume and warm-up

New or recently quiet mailboxes have little reputation. Sending a full cold campaign from them straight away is one of the fastest ways to end up in spam. Signs this is your problem:

• Placement was fine at low volume and dropped when you scaled
• Mailboxes went from zero to full volume in days rather than weeks
• One mailbox or domain is carrying most of the sending

Step 4: Check list quality

Sending to invalid or abandoned addresses produces bounces and can hit spam traps, both of which damage reputation. Verify every list before sending, remove hard bounces immediately, and never re-import addresses that have bounced or unsubscribed. A shared suppression list across all mailboxes stops an unsubscribed prospect from being contacted again from another domain.

Step 5: Check content and links

Content matters less than most people think, but some patterns do hurt:

• Link shorteners and shared tracking domains with poor reputations
• Several links or images in a first-touch email
• Attachments in cold emails
• Heavy HTML templates instead of plain, personal text
• Misleading subject lines or aggressive sales language

Keep first-touch emails short and plain, with at most one link, and use a custom tracking domain if you track clicks.

How multi-domain warming restores inbox placement

Multi-domain warming spreads your sending across several dedicated domains, each with a few mailboxes, and builds each mailbox's reputation gradually. It works for two reasons. First, no single mailbox sends enough to look suspicious. Second, if one domain runs into trouble, you can rest it while the others keep the campaign running.

Illustrative warm-up schedule for one new mailbox

WeekWarm-up emails per dayCold emails per dayWhat to watch15 to 100DNS and authentication passing210 to 200Warm-up messages landing in inbox315 to 205 to 10Bounces near zero, early replies4Keep running15 to 20Placement holding as volume rises5 onwardsKeep runningUp to your planned capWeekly reputation review

This is an example ramp, not a fixed rule. Slow down if placement drops at any stage, and keep warm-up running at a low level after cold sending starts.

Recovering a damaged domain

1. Stop cold sending from the affected domain immediately.
2. Fix the cause: authentication, list quality or volume.
3. Rest the domain for several weeks with only low-level warm-up activity.
4. Move live campaigns to healthy domains in the meantime.
5. If the domain stays blocklisted or its reputation does not recover, retire it.

For how we automate warming and monitor domain health continuously, see automating secondary domain warming and deliverability health monitoring. The rules large providers apply to high-volume senders are covered in our guide to navigating Google and Yahoo bulk sender guidelines without burning your domains.

Tighten DMARC once everything passes

Starting DMARC at p=none lets you collect reports without affecting delivery. Once the reports show every legitimate sending service passing, move to a stricter policy:

_dmarc.getacme.co.  TXT  "v=DMARC1; p=quarantine; rua=mailto:[email protected]; adkim=r; aspf=r"

The full specification is in RFC 7489.

Frequently Asked Questions

Why are my cold emails going to spam when SPF and DKIM pass?

Authentication is necessary but not sufficient. Check domain reputation, recent volume increases, bounce rates and whether the domain was warmed up properly. Content is usually the last thing to look at.

How long does it take to recover inbox placement?

It depends on how badly the domain was damaged. Lightly affected domains can recover within weeks of resting and gentle warm-up. Heavily damaged or blocklisted domains are often faster to replace than to repair.

Should we stop tracking opens?

Open tracking adds a tracking pixel and is less reliable than it used to be, because some mail clients load images automatically. Many teams turn it off for cold outreach and track replies instead. If you do track, use a custom tracking domain.

Do we need several domains for cold email?

If you send more than a small number of cold emails each day, yes. Spreading volume across several warmed domains keeps each mailbox within safe limits and limits the damage if one domain has problems.

Start with a quick audit

If cold emails are going to spam and you cannot pin down why, we can review your authentication, reputation signals, volumes and sending setup and give you a prioritised fix list. Our cold outreach and deliverability service covers the full setup, and you can ask our team for a deliverability review.

About the Author

Manav Sharma is the founder of Insyrge and a CRM solutions architect. He works across Zoho, Salesforce, HubSpot, Odoo and more, designing the CRM setups, integrations and automations that keep sales and operations teams working from the same data.