Zoho's limit is hourly, and it moves
Zoho Mail is the one major provider that publishes no daily cap. Its rates-and-limits page describes an external sending limit of 50 to 500 messages an hour that depends on the account's reputation with Zoho, 1,000 an hour internally, and 100 (free) or 150 (paid) external recipients per message. Exceed the hourly cap and the mailbox sees an “hourly quota exceeded” error until the window rolls. The practical consequence is unusual among providers: warming does not just build reputation with Gmail and Microsoft, it raises the limit Zoho itself applies to the mailbox.
Connect Zoho Mail: SMTP and IMAP with an app password
- 1
Generate an app password in Zoho
In the Zoho account's security settings, create an application-specific password for MailStrike. Your account password is never used.
- 2
Enter the SMTP and IMAP details
Zoho's SMTP server on port 587 with TLS, the IMAP server, the mailbox address and the app password. MailStrike verifies the connection on the spot.
- 3
Authentication checked on connect
SPF, DKIM, DMARC and MX for the domain are read as the connection lands. Zoho provides a DKIM selector in its admin console; if it is not published yet, the check returns the record.
- 4
Persona, volume, warming
A dedicated AI persona per mailbox and a daily volume with the plan default of 30. Warming mail is filed to a dedicated folder on arrival. Threads with the MailStrike network begin the same day, in your working hours.
The ramp against an hourly cap
The default 21-day ramp climbs to 30 warming emails a day per mailbox, spread across the persona's active hours. Even on day 21 that is a handful an hour, far inside the bottom of Zoho's range. How much warming to keep running once you start sending is below.
| Outreach a day, per mailbox | 1 mailbox | 2 mailboxes | 3 or more |
|---|---|---|---|
| Not sending yet | 30 | 21 | 18 |
| 10 emails | 30 | 21 | 18 |
| 20 emails | 25 | 18 | 15 |
| 30 emails | 20 | 14 | 12 |
| 40 emails | 15 | 11 | 9 |
| 50 emails | 10 | 7 | 6 |
The rule behind the table: a mailbox on its own that is not sending yet warms at the plan default of 30 a day, and once outreach starts it drops one warming email for every two you send, down to a floor of 10. Put a second mailbox on the domain and each one needs 70% of that figure, three or more and each needs 60%, because the domain earns the signal across all of them. Volume is a setting per mailbox, so you can dial these in directly.
Why bursts, not volume, trip Zoho
- A sequencer that sends in batches. Fifty emails in the first ten minutes of the hour is a burst; fifty spread across the day is not. On a new Zoho account at the bottom of the range, the burst hits the cap. Set the sequencer's send delay so real mail spreads out.
- Warming plus outreach in the same hour. Both count toward the external cap. Once the ramp is done, start real sending at 20 to 30 a day per mailbox and let warming settle to maintenance, around 15 to 25 a day.
- The receiving side is still Gmail and Microsoft. Zoho's cap is about Zoho. Where the mail lands is decided by the receivers, on the engagement history the warming network builds and the authentication Google's sender guidelines require.
After the ramp
That call belongs to the dashboard. Start at 20 to 30 a day per mailbox, keep the sends spread, and keep warming at maintenance so the reputation, and with it Zoho's hourly allowance, does not slide. A placement test before the first large send shows inbox, promotions or spam per receiving provider, which is the number that matters.
Questions about Zoho Mail warmup
What is the Zoho Mail sending limit?
Zoho publishes no fixed daily cap. Per its rates-and-limits page, external sending is limited per hour, between 50 and 500 an hour depending on the account's reputation, with 1,000 an hour internally; a message may carry 100 external recipients on a free account or 150 on a paid one. The limit rises as the mailbox's reputation with Zoho improves, which is why warming and the limit move together.
How does MailStrike connect to Zoho Mail?
Over SMTP and IMAP with an app password generated in Zoho, on port 587 with TLS. Authentication (SPF, DKIM, DMARC, MX) is checked on connect and any missing record comes back with the value to publish. Warming mail is filed to a dedicated folder on arrival so the real inbox stays clean.
Does warming raise the Zoho hourly limit?
Zoho scales the hourly cap with the account's reputation, so a mailbox that builds a clean sending record moves up the range. Warming builds exactly that record. It does not change the ceiling of 500 an hour, which no ramp approaches anyway.
What does 'hourly quota exceeded' mean on Zoho?
The mailbox sent more external mail in the rolling hour than its current reputation-based cap allows. Sending resumes when the window rolls over. A sequencer that sends in bursts will trip it on a new Zoho account; spread the sends and keep the total inside the ramp.
How long does a Zoho mailbox take to warm up?
MailStrike's default ramp reaches full volume in 21 days regardless of provider. The days-to-target measured for Zoho mailboxes is what the ramp study on this page will carry once it is published.