Benchmarks / Authentication

Do SPF, DKIM and DMARC improve cold email replies?

Based on 850 million+ emails · Smartlead platform data

Verified senders do better. Senders with SPF, DKIM and DMARC in place need about 108 contacts per reply, against 120 for unverified senders. That is 10% fewer contacts for each reply.

Check your setup

Are your sending domains set up with SPF, DKIM and DMARC?

Cold email replies by authentication

Contacts needed for each reply. Fewer is better. Built from more than 850 million emails sent through Smartlead.

Sender	Contacts per reply	Reply rate	Replies per 10,000 contacts
Verified (SPF, DKIM and DMARC)	108	0.93%	93
Unverified	120	0.83%	83

What the data shows

Verified senders win, but modestly. At 108 contacts per reply against 120, they need 12 fewer contacts for each reply.

At scale the gap adds up. Across 10,000 contacts, that is about 93 replies for verified senders against 83 for unverified ones.

The gap is smaller than the one between providers. Gmail senders need 90 contacts per reply and custom servers 179, a wider spread than the one between verified and unverified senders.

What Gmail and Outlook require

Google asks every sender to set up SPF or DKIM. Senders of more than 5,000 messages a day to Gmail accounts need SPF, DKIM and DMARC.

Microsoft requires SPF, DKIM and DMARC, with a policy of at least p=none, from senders of more than 5,000 emails a day to Outlook.com, Hotmail and Live addresses. Mail that fails can go to junk and later be rejected.

How this compares with common advice

Guides treat SPF, DKIM and DMARC as required, and for high-volume senders they are. Few put a number on the difference in replies. This data does. Verified senders need 10% fewer contacts per reply.

What this data can't tell you

It compares senders who authenticate with senders who don't, not the same campaigns before and after setup. Senders who skip authentication may differ in other ways, so the gap doesn't prove authentication alone causes it. It also doesn't split SPF, DKIM and DMARC apart or compare DMARC policy levels.

How to use these benchmarks

Set up all three records on every sending domain. The SPF, DKIM and DMARC guide walks through each one.
Check the records are live with the DMARC checker.
If you're new to DMARC, p=none is the minimum policy Outlook accepts.
Warm up after authenticating. The average sender warms up for 8 days before cold outreach.
Verify the list as well. The median sender bounces at 1.54%.

Frequently asked questions

Do I need SPF, DKIM and DMARC for cold email?

Yes. Google expects SPF or DKIM from every sender and all three from senders of more than 5,000 messages a day, and Outlook requires all three at that volume. In this data, verified senders also need about 108 contacts per reply against 120 for unverified ones.

Does DMARC improve deliverability?

The data doesn't isolate DMARC on its own. Senders with SPF, DKIM and DMARC in place need about 108 contacts per reply, against 120 for senders without them.

How much does missing authentication cost?

About 12 contacts per reply. Unverified senders need 120 contacts for each reply and verified senders 108, a gap of about 10 replies per 10,000 contacts.

Methodology

More than 850 million emails sent through Smartlead, using combined, anonymous platform data only. Only senders with at least 500 emails sent in the period are included. Verified senders have SPF, DKIM and DMARC set up on their sending domains. Contacts per reply is contacts emailed divided by replies.