Email warm-up and sending limits for a new mailbox
Start a new mailbox with a handful of real, one to one cold emails a day and raise the number slowly over a few weeks. A conservative pattern is about 5 a day in the first week, rising towards 20 a day per mailbox, while you watch bounces, spam complaints and replies. Set up SPF, DKIM and DMARC on your domain before the first send, verify every address, and slow down the moment bounces or complaints rise.
Why a new mailbox needs warming up
Mailbox providers judge a sender by its history. A new mailbox or domain has none, so a sudden burst of email to strangers looks like what spammers do. Sending a small, steady amount of relevant email that people open, reply to and do not report builds a reputation that later sends benefit from.
A conservative ramp
| Week | Cold emails a day | Move up only if |
|---|---|---|
| 1 | About 5 | Bounces are near zero and nobody has marked you as spam |
| 2 | About 8 to 10 | Replies are coming in and bounces stay low |
| 3 | About 12 to 15 | Same as above |
| 4 and later | Up to about 20 | Same as above; hold here rather than push higher |
Normal day to day email from the same mailbox (replies, internal mail) does not need to be counted against this, and it helps: it is the kind of two way traffic providers like. If you need more volume than about 20 cold emails a day, add another real person's mailbox rather than pushing one mailbox harder.
Provider sending limits are ceilings, not targets
Google documents a daily sending limit of 2,000 messages per user for paid Google Workspace accounts, lower during a trial, and 500 a day for a personal Gmail account. Going over a limit can lock sending for up to a day. These limits apply to all mail and are far above what a cold outreach mailbox should send. Microsoft 365 has its own limits; check its current documentation if you send from Outlook.
Set up SPF, DKIM and DMARC first
- SPF: a DNS record that lists which servers may send for your domain. For Google Workspace it includes _spf.google.com.
- DKIM: a signature that proves the message was not altered. In Google Workspace, generate a key in the Admin console and add the DNS record; until you do, mail is signed with a Google default domain instead of yours.
- DMARC: a DNS record that tells receivers what to do when SPF or DKIM fail and where to send reports. Start with p=none to monitor, then tighten.
Since February 2024, Google requires every sender to Gmail to use SPF or DKIM, keep the spam rate reported in Postmaster Tools below 0.3%, and use valid forward and reverse DNS. Senders of about 5,000 or more messages a day to Gmail must use SPF, DKIM and DMARC together and offer one click unsubscribe for marketing mail. Yahoo set similar rules. A small cold outreach mailbox is far below the bulk threshold, but setting all three up anyway costs little and helps.
What to watch while you ramp
| Signal | Healthy | Act when |
|---|---|---|
| Hard bounces | Close to zero | More than a couple per hundred: stop and clean the list |
| Spam complaints | Well under 0.1% | Approaching 0.3%: pause and rethink targeting and copy |
| Replies | Some, including no thanks | None after a few dozen sends: the targeting or message is off |
| Placement | Lands in the inbox in your own test accounts | Lands in spam: slow down and check authentication |
The bounce threshold is a common rule of thumb, not a published provider rule. The 0.3% spam rate is Google's published ceiling, and Google advises staying below 0.1%.
List quality matters more than warm-up
A perfect ramp cannot save a bad list. Guessed addresses bounce, and bounces damage reputation fast. Verify every address before sending, email only people for whom the message is relevant, and suppress anyone who unsubscribed or bounced, forever. Check the rules in the recipient's country too.
How Reach handles warm-up
Reach sends from your own Gmail mailbox, not a shared pool. Courier starts at 5 emails a day and rises to 20, Checker verifies every address twice, and sending stops for anyone who replies or unsubscribes. You approve every email first.
Checklist
- Add SPF, DKIM (with your own domain) and DMARC before the first send.
- Start around 5 cold emails a day per mailbox.
- Raise the daily number slowly, towards about 20.
- Verify every address and skip any that fail.
- Watch bounces, complaints and replies every day of the ramp.
- Pause at the first spike in bounces or complaints.
- Add mailboxes for more volume instead of pushing one harder.
- Suppress unsubscribes and bounces permanently.
Frequently asked questions
How many cold emails can a new mailbox send per day?
Start with about 5 a day and rise over a few weeks to about 20 per mailbox, as long as bounces and complaints stay low. Provider limits are much higher, but they are ceilings for all mail, not safe targets for cold outreach.
How long does email warm-up take?
Plan on three to four weeks of gradual increases for a new mailbox, longer for a brand new domain. Treat it as ongoing: reputation keeps depending on how recipients react.
What is the Gmail sending limit?
Google documents 2,000 messages a day per user for paid Google Workspace accounts, lower during trials, and 500 a day for personal Gmail. Check Google's current help page, as limits can change.
Do I need SPF, DKIM and DMARC for cold email?
Google requires at least SPF or DKIM for every sender, and all three for bulk senders. Set up all three: it is a one time DNS change and it helps delivery.
What spam complaint rate is too high?
Google asks senders to stay below 0.3% as reported in Postmaster Tools and advises aiming below 0.1%. For one to one cold email, complaints should be rare; any steady stream means the targeting is wrong.