Setting up custom sender domains in Mailtoaster for better deliverability

If your emails keep landing in spam—or if you're tired of looking like a hobbyist with “via mailtoaster.com” in your sender info—this guide’s for you. Setting up a custom sender domain in Mailtoaster isn’t tough, but doing it right makes a real difference. You’ll get better deliverability, look professional, and take control over your reputation. Let’s walk through it, step by step, and strip out the fluff.

Why bother with a custom sender domain?

Before you start fiddling with DNS records, know why this matters:

  • Boosts deliverability: Email providers care a lot about sender reputation. If you send from your own domain (set up correctly), you’re much less likely to end up in the spam folder.
  • Looks legit: No more “sent via mailtoaster.com.” Your recipients see you, not some third party.
  • Gives you control: You decide how emails are authenticated and tracked. If something's wrong, you can fix it.

The flip side? If you don’t set this up right, you can actually make things worse—think bounced emails or, worse, your domain being flagged as spammy. So don’t rush. Double-check each step.

What you need before you start

A little prep work saves a lot of headaches:

  • Access to your domain’s DNS settings. This is usually with your domain registrar (GoDaddy, Namecheap, Google Domains, etc.).
  • A verified Mailtoaster account. You’ll need to log in to Mailtoaster and have permissions to add sender domains.
  • Patience. DNS changes can take anywhere from a few minutes to a few hours to propagate. Don’t panic if things don’t work instantly.

Step 1: Add your domain in Mailtoaster

  1. Log in to Mailtoaster.
  2. Find the “Sender Domains” or “Domains” section (the UI changes now and then, but it should be somewhere in your account settings).
  3. Click “Add Domain” or “Verify New Domain.”
  4. Enter your domain name, without “http://” or “www.” For example: yourcompany.com

Mailtoaster will now show you some DNS records to add. Don’t close this tab—you’ll need it for the next step.

Step 2: Add DNS records (the crucial part)

Mailtoaster will typically ask you to add:

  • SPF Record (TXT): Authorizes Mailtoaster to send emails for your domain.
  • DKIM Record (CNAME or TXT): Cryptographically signs your emails, proving they’re really from you.
  • (Sometimes) DMARC Record (TXT): Tells inbox providers how to handle emails that fail SPF/DKIM checks.

How to add the records

  1. Log in to your DNS host’s dashboard (wherever you manage your domain’s DNS).
  2. For each record Mailtoaster provides:
  3. Copy the “Name” (sometimes called “Host” or “Label”).
  4. Copy the “Value.”
  5. Select the correct record type (TXT or CNAME).
  6. Paste the info and save.

Pro tip:
DNS dashboards are notoriously confusing. Sometimes you need to leave off the domain name in the “Name” field; other times you need to include it. If Mailtoaster says “add a TXT record for mailo._domainkey,” your DNS might want just mailo._domainkey or mailo._domainkey.yourcompany.com—check their help docs if in doubt.

What to ignore

  • MX Records: Unless Mailtoaster specifically asks, you don’t need to touch your MX records. Those are for receiving, not sending.
  • Wildcard SPF entries: Avoid using v=spf1 * or overly loose SPF records. They backfire and make your domain a spammer’s paradise.

Step 3: Verify your domain in Mailtoaster

  1. Go back to Mailtoaster and hit “Verify” or “Check DNS.”
  2. Wait a minute or two. If Mailtoaster says “verified,” you’re good.
  3. If it fails:
  4. Double-check for typos.
  5. Make sure you didn’t add extra spaces or periods.
  6. Remember, DNS changes can take time. Sometimes you just need to wait 30–60 minutes.

Honest take

DNS is the trickiest part of this whole process. Sometimes changes show up in five minutes, sometimes in three hours. If you’re stuck, try a DNS checker like MXToolbox to see what the world sees.

Step 4: Send a test email

Don’t just trust the green “verified” badge.

  1. Create a simple test campaign or transactional email to yourself (use Gmail, Outlook, and maybe Yahoo if you can).
  2. Check:
  3. Did it arrive in the inbox, spam, or promotions?
  4. Does the sender show as your domain, not “via mailtoaster.com”?
  5. If you view “original message” details, do you see “SPF: PASS” and “DKIM: PASS”?

If something’s off:
- SPF or DKIM fails? Double-check your DNS entries, including any old SPF records that might conflict. - Still hitting spam? Sometimes your content or sending behavior is the problem, not just your domain setup. Don’t buy lists or blast cold contacts.

Step 5: Set up DMARC (optional, but smart)

If you want extra protection—and to keep spoofers off your back—set up a DMARC record.

  1. In your DNS dashboard, add a TXT record:
  2. Name: _dmarc

  3. Value:

    v=DMARC1; p=none; rua=mailto:your@email.com

  4. Replace the email with your own (you’ll get reports).

  5. Once you know SPF and DKIM are working, you can get stricter:

  6. Change p=none to p=quarantine (send failures to spam) or p=reject (block failures).

But—don’t rush to “reject” unless you’re sure all your mail sources are set up correctly. Otherwise, you’ll lose legit emails.

Troubleshooting: Common headaches (and what to do)

  • Mailtoaster won’t verify my domain:
  • Wait an hour, then check again.
  • Use an external tool to see your DNS records.

  • Watch out for typos, missing dots, or wrong record types.

  • SPF/DKIM passes, but emails still land in spam:

  • Your sending reputation may be shot. Warm up your domain if it’s brand new—start slow.
  • Check your content for spammy phrases (“free money!” isn’t helping).

  • Make sure you’re not blasting to stale or purchased lists.

  • Multiple SPF records:

  • You can only have one SPF record per domain. If you need to add Mailtoaster to an existing one, combine them:

    v=spf1 include:mailtoaster.com include:other-service.com ~all

What’s worth your time (and what’s not)

  • Worth it:
  • Setting up SPF, DKIM, and DMARC. Yes, it’s a pain, but it’s the price of entry for good deliverability.
  • Testing with real inboxes, not just the built-in “test” button.

  • Keeping your sender lists clean.

  • Not worth it:

  • Obsessing over fancy DNS settings or trying to “hack” inbox placement with weird tricks.
  • Paying for “deliverability boosters” before you’ve nailed the basics.

Keep it simple, check your work, and iterate

Getting custom sender domains working in Mailtoaster isn’t rocket science, but it does take a careful touch. Don’t make it harder than it needs to be—set up SPF, DKIM, and (eventually) DMARC, send real test emails, and check that things work. If you hit a wall, take a break and come back with fresh eyes. Nearly every deliverability horror story boils down to a tiny DNS typo or skipping a test.

Set it up, keep it tidy, and don’t overthink. Better deliverability is about doing the basics well, not chasing silver bullets.