Gmail · Google Workspace
Cold email from Gmail, done carefully.
Connect any Gmail or Workspace mailbox with an app password. Mailnitrix sends through Google's own servers, warms the mailbox up and keeps it well inside safe limits.
Setup
Connected in about five minutes.
- 01
Turn on 2-Step Verification
Google only offers app passwords on accounts with 2-Step Verification switched on.
- 02
Create an app password
In your Google Account, open App passwords, name it Mailnitrix and copy the 16-character password.
- 03
Add the mailbox
Enter your address and the app password. Mailnitrix fills in smtp.gmail.com (587) and imap.gmail.com (993).
- 04
Test and tune
Run the connection test, set a daily limit and switch on warmup if the mailbox is new.
Built for Gmail
What Mailnitrix does for Gmail mailboxes.
- Sends from your real account, so replies land in your Gmail
- Warmup reports Inbox, Spam and Promotions placement
- Spam rescue moves warmup emails back to the inbox
- Reads Google's error codes and cools the mailbox down the right way
- Mixes with Outlook mailboxes in the same campaign
Before you send
Set up your domain.
- SPF: authorise Google to send for your domain
- DKIM: turn on signing in the Workspace admin console
- DMARC: publish at least a p=none policy
- Use a separate domain for outreach to protect your main one
Error codes
When Google says no.
These are the Gmail responses cold emailers see most, and what each one means.
| Response | What it means and what to do |
|---|---|
535 5.7.8 Username and Password not accepted | Google rejected the password. Use an app password, not your normal password, and create a new one if it was revoked. |
534 5.7.9 Application-specific password required | 2-Step Verification is on, so Google needs an app password. Create one and paste it into Mailnitrix. |
550 5.4.5 Daily user sending limit exceeded | The mailbox hit Google's daily cap. Mailnitrix rests it for 24 hours and moves its emails to other mailboxes. |
421 4.7.28 Unusual rate of unsolicited mail | Google is throttling the mailbox. Mailnitrix pauses it for an hour, longer on repeats. Lower its daily limit. |
550 5.7.1 Message likely unsolicited mail | Blocked as spam. The mailbox pauses for 6 hours. Check your domain's SPF, DKIM and DMARC, your list quality and your copy. |
FAQ
Gmail questions.
Why an app password instead of signing in with Google?
App passwords let Mailnitrix send and run warmup over Google's standard SMTP and IMAP servers without broader access to your Google account. You can revoke an app password at any time from your Google Account.
How many emails can a Gmail mailbox send?
Google's published limit for Workspace users is 2,000 messages a day (500 on trial accounts), and personal Gmail accounts are lower. Those are ceilings, not targets: for cold email, keep each mailbox to about 30 to 40 a day once it's warmed up.
Can I use free @gmail.com addresses?
Yes, they connect the same way. For serious outreach, Workspace mailboxes on your own domain are better: you control SPF, DKIM and DMARC and your brand is on every email.
My Workspace mailbox won't connect. What now?
Your admin may have restricted app passwords or IMAP for the organisation. Ask them to allow both for the mailboxes you use with Mailnitrix.
Start sending smarter, for free.
1,000 emails every month on the free plan. No credit card, no time limit.