Each mailbox type in Icemail has specific sending limits. Understanding these limits helps you build a scalable, deliverable cold email infrastructure.
Sending Limits by Mailbox Type
Google & Microsoft Mailboxes
Cold emails: 15 per mailbox per day
Warmup emails: 15 per mailbox per day (1:1 ratio with cold emails)
Total maximum: 30 emails per mailbox per day
SMTP Mailboxes
50 emails per mailbox per day
Azure Mailboxes
10 emails per mailbox per day total
Recommended split: 5 cold emails + 5 warmup emails
What Happens When You Hit Sending Limits
Exceeding sending limits can have serious consequences:
Google or Microsoft may flag your account for unusual sending behavior
Bounce rates increase as sending volume outpaces your reputation
Spam complaint rates rise, hurting future deliverability
In severe cases, the mailbox may be suspended
Recovering From Limit Violations
If you’ve sent too many emails from a mailbox:
Reduce volume immediately — stop all cold email sending
Pause cold outreach for at least 48 hours
Continue warmup emails only during the recovery period
Gradually resume cold sending at a lower volume
How to Scale Without Hitting Limits
The correct way to scale cold email volume is with more domains and mailboxes, not by pushing individual mailbox limits:
Use 2–3 mailboxes per domain
Add more domains to increase total sending capacity
Example: 100 emails/day = 4 mailboxes x 25 emails each (well within limits)
Handling Failed Emails
If emails fail or bounce:
Check your outreach tool’s failed/bounced log to identify affected emails
Do not immediately retry failed emails — this can worsen your reputation
Wait at least 24 hours before retrying, and only retry if the failure was a temporary issue
Questions About Sending Strategy?
Contact team@icemail.ai for guidance on structuring your sending infrastructure for scale.