Service policy

Terms and Conditions

These terms explain the rules for using KKCSI services, including acceptable use, server resources, email and forwarding, payments, refunds, and account cancellation.

Applies to: KKCSI customers and account usersLast updated: 15 October 2026

Use services responsiblyIllegal activity, abuse, spam, phishing, malware, and attempts to evade safeguards are prohibited.

Keep accounts secureCustomers are responsible for credentials, valid recipients, billing details, and activity performed through their accounts.

Protect shared systemsWe may defer, restrict, suspend, or terminate activity that threatens service stability, security, or delivery reputation.

01Acceptable Use

Customers must use our services in accordance with all applicable laws and the acceptable-use rules of any network connected to our systems. We may cooperate with law-enforcement agencies when legally required.

Content stored, published, or distributed through an account must not infringe copyright, trademark, patent, privacy, statutory, common-law, or other proprietary rights. Obscene, defamatory, or unlawful material is prohibited. Hardcore adult or pornographic websites may not be hosted on shared or reseller servers.

Prohibited conduct

Unsolicited bulk email, abusive mass messaging, phishing, malware, or use of purchased mailing lists.
Repeated off-topic or excessive newsgroup posting, including substantially similar posts to 20 or more groups.
Using an account as a mail drop for abusive activity conducted through another provider.
Harassment, impersonation, falsifying sender identity, or misrepresenting an account user.
IRC abuse tools, flooding or attack scripts, unauthenticated open proxies, open mail proxies, or software intended to facilitate abuse.

Enforcement: Suspected abuse may result in immediate restriction or suspension while we investigate. Confirmed serious or repeated violations may result in termination. Customers may be responsible for reasonable cleanup and complaint-handling costs caused by their activity.

02Server Resources

Shared services must be used fairly. We may stop processes or restrict an account when its activity affects server stability or other customers.

Resource	Standard limit
CPU or memory	No more than 50% of available resources for longer than 30 seconds; daily usage should not exceed 2% CPU or 3% memory.
Processes	No more than 10 simultaneous processes per user, 30 CPU seconds per process, or 32 MB memory per process.
Database connections	Maximum 16 concurrent user connections.
Cron jobs	No more frequently than once every 30 minutes unless the software provider specifically requires otherwise; jobs may be assigned a lower processing priority.

Where a plan specifies different limits, the limits stated for that plan apply.

03Email Sending and Forwarding

Email usage is measured by recipient delivery. A single message sent or forwarded to multiple recipients counts once for each recipient. Addresses entered in the To, CC, and BCC fields are treated equally for limit calculations; using BCC does not bypass any sending limit.

Sending limits

Scope	Limit
Recipients per message	Maximum 50 recipients in total, including all To, CC, and BCC addresses.
Mailbox burst limit	100 recipient deliveries per 10 minutes. Additional recipients are temporarily deferred and may be retried later.
Authenticated sending source	500 recipient deliveries per hour from a source public IP address.
Authenticated mailbox	500 recipient deliveries per hour, regardless of the number of devices or source connections used.
Mailbox	5,000 recipient deliveries per day.
Hosting account	5,000 recipient deliveries per day.
Invalid recipients	An authenticated mailbox may be automatically blocked after 10 invalid recipient attempts within one hour.

Forwarding monitoring and limits

Updated 16 October 2026: forwarding volume thresholds are monitoring alerts, not automatic rejection limits. Reaching these thresholds alone does not stop incoming mailbox delivery or forwarding.

Scope	Monitoring threshold
Each forwarder	10 external deliveries per 5 minutes, 50 per hour, and 300 per day.
Gmail destinations	200 forwarded deliveries per hour across the server.
Microsoft destinations	100 forwarded deliveries per hour across the server.
All external destinations	300 forwarded deliveries per hour across the server.
External destinations per forwarder	The existing maximum of 2 external destinations for new or modified forwarders remains applicable. Locally hosted destinations do not count toward this maximum.

Spam filtering, authenticated sending limits, attachment checks, invalid-recipient controls and abuse restrictions still apply. Receiving providers may independently delay, reject or classify mail as spam.

Delivery protection

Authenticated SMTP submission is permitted only over encrypted connections on the designated submission ports. Authentication is not offered on the normal server-to-server SMTP port.
Authenticated senders may only use an authorised sender address or domain associated with their hosting account. Sender spoofing is blocked.
Authenticated outbound messages are checked by the server's spam filter. A message with a high spam score may be rejected before delivery.
Dangerous executable attachment types, including dangerous files found inside supported archives, may be rejected.
The maximum accepted message size is 35 MB, including headers and encoding overhead. The original attachment must therefore be smaller; use a secure file-sharing link for large files.
Sender Rewriting Scheme (SRS) is used for forwarded mail where applicable.
Messages identified as spam may not be forwarded externally.
To, CC, and BCC are all counted from the SMTP envelope, including addresses that are not visible in the received message header.
An authenticated mailbox may be automatically blocked after 10 invalid recipient attempts within one hour and will require review before sending resumes.
An external destination may be suspended after three permanent recipient failures within 24 hours, including an inactive, disabled, unknown, or non-existent mailbox.
Full or over-quota destination mailboxes: When an external forwarding destination (such as a remote Gmail address) rejects delivery with an out-of-storage error (e.g., SMTP 452 4.2.2 The recipient's inbox is out of storage space), delivery retries to that recipient stop immediately rather than keeping messages queued for up to 4 days. Customers must ensure forwarded recipient mailboxes have sufficient available storage or remove full/abandoned forwarder destinations.
When a limit is reached, delivery may be temporarily deferred or held so the sending server can retry later.

Important: These are safety ceilings, not guarantees that a receiving provider will accept or deliver a message. Repeated spam, abnormal volume, compromised credentials, excessive bounces, complaints, or attempts to bypass controls may lead to a longer hold or suspension.

Delivery notices and email policy codes

When authenticated SMTP email breaks a sending rule, our server returns a delivery-status response to the submitting mail application or sending server. The response identifies the applicable policy code, the limit reached, the reason for the restriction, and a suggested corrective action. The submitting software normally displays this response directly or includes it in a delivery-failure notice to the sender.

How to read the returned error: The standard SMTP number and the KKCSI policy code appear together, for example 451 4.7.1 — EMAIL-R02. The SMTP number is not a second policy-code system. 451 means a temporary delay that normally retries automatically; 550 means the message was rejected and the stated problem must be corrected before sending again.

EMAIL-R01 — Too many recipients in one message

SMTP 550 5.7.1 — Permanent rejection

Why it happened: One message contained more than 50 combined To, CC, and BCC recipients.

Simple example: You send one email to 20 To addresses, 20 CC addresses, and 15 BCC addresses. That is 55 recipients, so the message is rejected.

What to do: Split the recipients into groups of 50 or fewer and send again. Use a proper mailing-list platform for newsletters.

Provider responses you may seeGmail452 4.5.3 or 550 5.5.3 — too many recipients.Microsoft4.5.3 or 5.5.3 — too many recipients.Split the recipient list into smaller groups.

EMAIL-R02 — Too many recipients within 10 minutes

SMTP 451 4.7.1 — Temporary delay

Why it happened: One authenticated mailbox attempted more than 100 recipient deliveries during a rolling 10-minute period.

Simple example: You send four messages to 30 people each within a few minutes. That creates 120 recipient deliveries, even though only four messages were sent.

What to do: Stop sending for at least 10 minutes. Most mail applications retry automatically, so do not keep pressing Send.

Provider responses you may seeGmail450 4.2.1 421 4.7.28 550 5.7.1 — rapid or unusual sending.Microsoft432 4.3.2 4.7.500–699 4.7.850–899 5.2.121 5.2.122 — rapid sending or throttling.Pause sending and allow automatic retry.

EMAIL-R03 — Hourly mailbox limit reached

SMTP 451 4.7.1 — Temporary delay

Why it happened: One authenticated mailbox attempted more than 500 recipient deliveries within a rolling hour.

Simple example: Ten messages sent to 50 people each use all 500 hourly recipient deliveries. The next recipient is temporarily deferred.

What to do: Pause sending for up to one hour and allow queued messages to retry. Use a bulk-email service for campaigns or announcements.

Provider responses you may seeGmail421 4.7.28 or 550 5.7.1 — unusual rate or rate limiting.Microsoft5.2.121 5.2.122 4.7.500–699 4.7.850–899 — hourly or temporary restriction.Reduce the hourly sending rate.

EMAIL-R04 — Mailbox blocked after invalid recipients

SMTP 550 5.7.1 — Security rejection

Why it happened: The mailbox attempted delivery to 10 invalid or non-existent recipients within one hour. This can indicate an outdated list, an incorrectly configured program, or a compromised password.

Simple example: An old contact list contains 10 addresses belonging to former employees. Repeated attempts to those addresses trigger the security block.

What to do: Stop automated sending, remove invalid addresses, change the mailbox password, check connected devices or scripts, and contact the hosting administrator for review.

Provider responses you may seeGmail550 5.1.1 553 5.1.2 553 5.1.3 550 5.2.1 — invalid, missing, or inactive recipient.Microsoft5.1.1 5.1.10 5.4.1 550 5.5.0 5.7.504 5.7.505 — recipient not found or rejected.Correct or remove the invalid address before trying again.

EMAIL-R05 — Message scored as high-risk spam

SMTP 550 5.7.1 — Content rejection

Why it happened: The outbound message received a spam score above 12.0 because its content, links, formatting, or sending behaviour resembled spam or phishing.

Simple example: A message contains several shortened links, urgent payment wording, a suspicious attachment, and very little normal text.

What to do: Confirm the account is secure, remove suspicious links or attachments, rewrite misleading wording, and send only to people who agreed to receive the message.

Provider responses you may seeGmail421 4.7.0 421/550 4.7.28 552 5.7.0 550 5.7.1 5.7.26–5.7.30 5.7.40 — spam, reputation, content, or authentication.Microsoft4.7.500–699 5.1.8 5.7.501–503 5.7.509 5.7.606–649 5.7.705/708 5.7.800 — spam, compromised sender, DMARC, IP, or tenant restriction.Stop sending, secure the account, and fix content or authentication.

EMAIL-R06 — Daily hosting-account limit reached

SMTP 451 4.7.1 — Temporary delay

Why it happened: All mailboxes under one hosting account collectively reached 5,000 recipient deliveries during the daily usage window.

Simple example: Five staff mailboxes each deliver 1,000 recipient copies in one day. Together they reach the account's 5,000-delivery ceiling.

What to do: Stop sending and wait for the daily window to reset. Moving to another mailbox under the same account will not bypass this limit.

Provider responses you may seeGmail550 5.4.5 — daily user or relay limit.Microsoft5.1.90 5.2.2 5.7.233 — recipient, submission, or tenant daily limit.Wait for the daily window to reset and investigate unexpected volume.

EMAIL-R07 — Daily mailbox limit reached

SMTP 451 4.7.1 — Temporary delay

Why it happened: One mailbox reached 5,000 recipient deliveries during the daily usage window.

Simple example: A mailbox sends 100 separate messages to 50 recipients each. That equals 5,000 recipient deliveries.

What to do: Wait for the daily window to reset and do not repeatedly resend. Use a bulk-email platform if this volume is part of normal business activity.

Provider responses you may seeGmail550 5.4.5 — daily user or relay limit.Microsoft5.1.90 or 5.2.2 — recipient or submission quota exceeded.Wait for the limit window to reset; do not switch devices or repeatedly resend.