Configuration Reference — Cloud Server for Email

DOCUMENTATION

Adjustable parameters and how to request configuration changes

This reference covers the PowerMTA and MailWizz configuration parameters available in your managed infrastructure. All configuration changes are applied by the Cloud Server for Email team — contact infrastructure@cloudserverforemail.com to request any adjustment.

PowerMTA Domain Block Parameters

Parameter	Default (Production)	Range	When to Request Change
max-smtp-out	5–10 per ISP	1–20	Reduce if deferral rate >10%; increase after sustained HIGH reputation
max-msg-rate	800–3,500/h per ISP	Unlimited	Reduce if deferral spikes; increase gradually as reputation improves
retry-after	15–30m per ISP	5m–12h	Increase if ISP hints longer retry interval in 421 response
max-msg-per-conn	30–100 per ISP	1–200	Rarely needs changing; adjust if session-termination bounces appear
dkim-sign	yes (all domains)	yes/no	Always yes; disable only for specific diagnostic testing

Adding a New Sending Domain

Email infrastructure@cloudserverforemail.com with the new domain name
We generate DKIM key pair and provide the DNS TXT record
Add the DKIM record to the new domain DNS
Add the new domain IPs to your SPF record
We configure PowerMTA domain block and MailWizz sending domain

MailWizz Key Settings

Setting	Location	Notes
Suppression list	Lists → Subscriber suppression	Add hard bounces and complaints; global list applies to all campaigns
Bounce server	Backend → Servers → Bounce servers	Must be active; we configure IMAP connection during onboarding
Tracking domain	Backend → Settings → Tracking	Custom domain with SSL; configured during onboarding
Campaign hourly quota	Campaign → Sending quota	Must not exceed PowerMTA max-msg-rate for that ISP
Cron schedule	Server crontab	Every 5 minutes; do not modify without consulting us

Requesting Configuration Changes

To: infrastructure@cloudserverforemail.com
Subject: Configuration Change Request

Parameter: max-smtp-out (gmail.com)
Current value: 8
Requested value: 6
Reason: Gmail deferral rate elevated (12%) over last 3 days
Accounting log attached: [attach excerpt]

We review and apply configuration changes within 24 business hours. Changes affecting delivery behavior are monitored for 2–4 hours after application.

Direct Configuration Access

Enterprise tier clients receive SSH access to their server. However, direct edits to /etc/pmta/config should be coordinated with the Cloud Server for Email team to avoid conflicts with monitoring and management systems.