Benchmarks / Gmail vs Outlook

Does Gmail or Outlook get more cold email replies?

Based on 850 million+ emails · Smartlead platform data

Gmail. Gmail senders need about 90 contacts per reply, against 120 for Outlook and 179 for custom servers. That means Gmail needs 25% fewer contacts per reply than Outlook, and about half as many as a custom server.

Cold email replies by sending provider

Contacts needed for each reply, by the provider the mailbox sends from. Fewer is better. Built from more than 850 million emails sent through Smartlead.

Provider	Contacts per reply	Reply rate	Replies per 1,000 contacts
Gmail	90	1.11%	11
Outlook	120	0.83%	8
Custom servers	179	0.56%	6

What the data shows

Gmail leads. Gmail senders get a reply every 90 contacts, a reply rate of about 1.11%.

Outlook is close behind. At 120 contacts per reply, Outlook senders need a third more contacts than Gmail senders for each reply.

Custom servers trail both. At 179 contacts per reply, they need about twice as many contacts as Gmail.

The gap doesn't show up in warmup. Warmup emails reach the inbox about 99% of the time on all three, with Outlook at 99.0%, Gmail at 98.8% and custom servers at 98.8%.

How this compares with common advice

Most comparison guides call Gmail and Outlook roughly equal for cold email, or give Gmail a slight edge, and back it with sending limits and prices rather than reply data. This data puts a number on the edge. Gmail senders need 25% fewer contacts per reply than Outlook senders.

What this data can't tell you

It compares senders by provider, not the same emails sent from each. Senders who pick Gmail may differ from those who pick Outlook in list, market or volume, so the gap doesn't prove the provider causes it. The data also doesn't split results by the recipient's provider.

How to use these benchmarks

If you are choosing a provider for new mailboxes, Gmail has the edge in this data. The Google Workspace vs Office 365 guide covers setup and cost.
If you send from a custom server, judge your results against 179 contacts per reply, not Gmail's 90.
Authenticate every domain, whichever provider you use. Verified senders need 108 contacts per reply against 120 for unverified ones.
Keep daily volume near the norm. The median mailbox sends about 14 cold emails a day.
If you need new mailboxes, you can buy email accounts that come fully set up.

Frequently asked questions

Is Gmail or Outlook better for cold email?

Gmail, in this data. Gmail senders need about 90 contacts per reply and Outlook senders about 120, so Gmail needs 25% fewer contacts for each reply.

Can I use a custom mail server for cold email?

You can, but custom servers trail both big providers here. They need about 179 contacts per reply, about twice as many as Gmail.

Does the email provider affect reply rates?

Senders on different providers get different results. Gmail senders need about 90 contacts per reply, Outlook senders 120 and custom servers 179. The data can't show how much of that gap comes from the provider itself.

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. Senders are grouped by the provider their mailboxes send from. Contacts per reply is contacts emailed divided by replies, and reply rate is its inverse.