Zendesk email from your own brand, not Zendesk's

Your support emails say “From: Your Company” but they’re signed by Zendesk. When a customer gets a ticket notification from support@yourcompany.com, Gmail checks the DKIM signature — and it’s zendesk.com, not yourcompany.com. DMARC alignment fails. The email lands in spam. The customer never sees the resolution.

This is the default for every Zendesk instance. Zendesk sends through its own SMTP infrastructure, and there’s no built-in option to use your own DKIM key. For most support teams, it’s invisible — until deliverability matters.

MailKite fixes this. One SMTP setting change and every Zendesk email is signed with your key, from your domain, with full deliverability logs.

What Zendesk’s default email does

When an agent replies to a ticket, Zendesk sends the email through its own mail servers:

1. The From address is your support address (e.g., support@yourcompany.com)
2. The DKIM signature is Zendesk’s (zendesk.com)
3. The Return-Path bounces to Zendesk’s domain
4. SPF checks Zendesk’s IP against your SPF record — which doesn’t include it

Result: DMARC fails alignment. Gmail may route the email to spam, especially for recipients at strict DMARC domains (government, enterprise, education).

The fix: one SMTP setting

1. Verify your domain in MailKite

Add yourcompany.com to the MailKite dashboard. Publish the DNS records (MX, SPF, DKIM, DMARC). Under 5 minutes.

2. Configure Zendesk’s outbound email

In Zendesk Admin, go to Channels → Email and edit your support address. Change the SMTP settings:

Setting	Value
SMTP server	smtp.mailkite.dev
Port	587
Username	mailkite
Password	Your API key (mk_live_…)
Authentication	PLAIN (over TLS)
TLS	Yes (STARTTLS)

Set the From name to your brand and the From address to an address on your verified domain.

3. Verify

Send a test ticket reply. Check the headers in Gmail:

Authentication-Results: mx.google.com;
  dkim=pass header.d=yourcompany.com
  spf=pass
  dmarc=pass

All three pass. The email is signed with your key.

What gets sent through MailKite

Once configured, every Zendesk email routes through MailKite:

• Ticket auto-replies — “We got your request” emails
• Agent replies — responses to customer issues
• Internal note notifications — agent-to-agent alerts
• Satisfaction surveys — CSAT/NPS emails after resolution
• Trigger-based emails — any custom trigger that sends email

All DKIM-signed, all logged in the MailKite dashboard, all with the same deliverability guarantees as API sends.

Receiving inbound email → Zendesk tickets

Zendesk has a unique inbound address per ticket (e.g., support+ticketid@yourdomain.zendesk.com). If you use MailKite for inbound, you can pipe customer replies back into Zendesk via the API:

// zendesk-webhook.js — receives inbound email, adds comment to ticket
export default {
  async fetch(request, env) {
    if (request.method !== "POST") return new Response("OK");

    const payload = await request.json();
    const { from, subject, text, inReplyTo } = payload;

    // Extract ticket ID from subject or headers
    let ticketId;
    if (inReplyTo) {
      const match = inReplyTo.match(/ticket[_-]?(\d+)/i);
      if (match) ticketId = match[1];
    }
    if (!ticketId) {
      const match = subject.match(/#(\d+)/);
      if (match) ticketId = match[1];
    }
    if (!ticketId) return new Response('{"ok":true}', { status: 200 });

    // Add comment to the ticket
    const res = await fetch(
      "https://" + env.ZENDESK_SUBDOMAIN + ".zendesk.com/api/v2/tickets/" + ticketId + ".json",
      {
        method: "PUT",
        headers: {
          Authorization: "Bearer " + env.ZENDESK_API_TOKEN,
          "Content-Type": "application/json",
        },
        body: JSON.stringify({
          ticket: {
            comment: {
              body: "From: " + from + "\n\n" + text,
              public: false,
            },
          },
        }),
      }
    );

    return new Response(JSON.stringify({ updated: res.ok }), { status: 200 });
  },
};

Customer replies are added as internal comments on the matching ticket — visible in the agent workspace, tied to the right conversation.

Multiple brands

Zendesk supports multiple brands with different email addresses. Each brand can have its own From address on a different verified MailKite domain. They all share the same API key and logs, so you manage one account across all brands.

How it compares

	Zendesk default email	Zendesk + MailKite SMTP
DKIM signature	Zendesk’s key	Your key
SPF alignment	Fails	Passes
DMARC alignment	Fails	Passes
Sending reputation	Zendesk’s shared pool	MailKite dedicated
Delivery logs	Zendesk’s email tab	MailKite dashboard + API
Inbound parsing	Email-to-ticket (basic)	Webhook → structured JSON
Multi-brand	Same SMTP for all	Per-domain DKIM signing

FAQ

Will this break Zendesk’s email features? No. Zendesk’s email features (triggers, automations, macros) all use the configured SMTP server. MailKite is a drop-in replacement — same SMTP interface, different backend.

What about Zendesk’s Chat and Messaging channels? Those don’t use email — they’re real-time channels. MailKite only affects email-based ticket notifications and agent replies.

Can I use MailKite for inbound and Zendesk for outbound? Yes. You can split the configuration: MailKite’s inbound webhooks for receiving email at your domain, and Zendesk’s default SMTP for outbound. But using MailKite for both gives you consistent DKIM signing and a single delivery pipeline.

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Related: HubSpot transactional email — the same pattern for CRM email · Salesforce email relay — for Salesforce orgs · Receive email as a webhook in Python — building custom inbound handlers