Skip to main content
Deliverability is whether your email actually reaches the inbox. Custral inherits the deliverability profile of the underlying mailbox you’ve connected. Custral does not relay through its own SMTP, so your reputation stays with you. The goal of this guide is to surface the levers that affect inbox placement and the diagnostics Custral exposes.

​
The three records that matter

1

SPF, who is allowed to send for your domain

A TXT record on your domain that lists the IPs / providers permitted to send mail with your From: address. Most issues come from missing include: entries when adding a new sending provider.
2

DKIM, cryptographic signature on each message

A public key published on a ._domainkey. subdomain. Each outbound message is signed; receivers verify the signature against the published key. Without DKIM, forwarded messages are routinely rejected.
3

DMARC. What receivers should do when SPF or DKIM fails

A TXT record at _dmarc.<domain> that tells receiving servers whether to quarantine or reject mail that fails alignment. A p=reject policy is strict but is increasingly required by major mailbox providers.

​
Diagnostics

Custral surfaces deliverability signals on each Channel:
  • The last 50 inbound delivery reports (provider IDs + status).
  • Per-domain bounce and complaint rates over the last 30 days.
  • Whether the channel’s domain has SPF / DKIM / DMARC published correctly (a DNS check refreshed daily).

​
Sender reputation

Reputation is per-sending-IP and per-domain. Sending from a brand-new domain with high volume is the fastest way to be flagged as a spammer, warm a domain by ramping volume gradually over 2-4 weeks.

​
What to do when delivery degrades

If your bounce rate climbs above ~5% or your complaint rate above 0.1%, mailbox providers will start to throttle. Pause outbound sequences, audit your list for stale addresses, and remove anyone who hasn’t engaged in 90+ days.
  • Remove suppressed addresses (see Suppressions).
  • Review your unsubscribe link. Every campaign email must carry one.
  • Slow down sending and let reputation recover before resuming.

​
Configuring domains in Custral

Sending domains are managed from the Domains settings screen. It has up to two tabs:

Active Domains

A card per domain showing verification status, mailboxes, DNS setup, health score, and per-domain actions.

Health & Deliverability

Per-channel health scores and Gmail / Outlook inbox-placement bars. Admin-only.
Adding domains (Buy Domain / Connect Existing Domains) and the Health & Deliverability tab are admin-only. They appear only when your account has admin access. Non-admins still see the Active Domains list and can verify, add mailboxes, and view DNS records.

​
Adding a domain

From the header, click Buy Domain. Search for a domain name; results show Available / Unavailable with a per-domain Buy action priced in credits. Purchasing registers the domain as a Custral Managed domain and begins configuration.
A newly purchased domain shows a Registering state while registration completes. DNS setup becomes available once registration finishes (usually 5–30 minutes).

​
The domain card (Active Domains)

Each domain card surfaces:

​
Card actions

Re-checks verification with the provider. Before verification this is a Verify Domain button; once active it becomes a Sync Status refresh icon. Verification depends on DNS propagation, so it may report “still pending.”
Opens the Add Mailbox modal (see below).
From the card’s overflow menu (⋮), makes this the primary sending domain.
For Custral-managed domains, opens a viewer of the current DNS record set, with a Clear DNS action.
Admin-only, in the overflow menu. Disabled for the primary domain and for any domain that still has mailboxes. Delete its mailboxes first.

​
DNS records & sync

The DNS info icon opens DNS Records for <domain>, listing each record’s type, name, value (with Copy Value), and a verification status badge. DNS records are fetched on demand when the modal opens. Add these records at your registrar (Google, GoDaddy, Cloudflare, etc.) to verify ownership and enable sending. For Custral-managed domains, the records modal also offers:
Clear DNS removes records from the managed DNS zone and can break sending and verification for that domain. Only use it when you intend to rebuild the zone.

​
Adding a mailbox

The Add Mailbox modal creates a new Custral-managed mailbox on the domain (it includes a calendar reachable from the calendar UI):
  • Account Name: a display label for the mailbox.
  • Local Part: the part before @<domain> (the modal shows the full address inline).
  • Assign to User (Optional): pick an owner.
To edit an existing mailbox, use its overflow menu → Edit / Assign User, which exposes the mailbox name / email and owner, Manage Assignments (share the inbox with additional users / teams), routing rules, and a connection health panel with a Test connection button. Use it when sends or syncs look stuck.

​
Warming settings (deliverability ramp)

Open a mailbox’s overflow menu → Warming Settings. Every user sees Account Name, Sender Display Name (the name recipients see on warming emails), and Enable Email Warming (the on/off toggle).
Volume limits and the ramp rate are managed by Custral rather than set per mailbox. Warming works best on a schedule tuned to a domain’s age and reputation. Ask support if you need a ramp faster or slower than the default.

​
Health & Deliverability tab

This admin-only tab shows, per domain, each channel’s Health score and Gmail / Outlook inbox-placement percentages (inbox vs. total), plus a Warming Active badge and today’s warming usage vs. the current limit when warming is on.

​
Troubleshooting