Use Your Own SMTP Provider with TrekMail

TrekMail can deliver outgoing mail through a provider you already use, such as Amazon SES, SendGrid, Mailgun, Mailjet, or another SMTP service. SMTP simply means the service that sends the message to the recipient.

Who this is for

• Nano Plan Users: This is required to send outbound mail.
• High Volume Senders: If you need to send millions of emails cheaper than our plans allow.
• Businesses with an existing provider: Keep the delivery service and reputation you already use.
• Different brands or clients: Send each domain, or even one connected-inbox From address, through the right provider.

How it works

Custom SMTP is normally configured per domain. Picking a provider for a domain tells TrekMail: "When I send from this domain, deliver the message through this service."

• Per domain: Each domain points at its own route. You can run one domain on your own provider and another on managed SMTP.
• Reusable profiles: A custom SMTP connection is saved as a profile on your account. Once saved, you can reuse the same profile across multiple domains instead of re-entering credentials each time.
• Webmail: Uses the domain's saved credentials to send.
• Desktop Clients (Outlook): You should usually enter your provider's SMTP settings directly into Outlook, bypassing TrekMail entirely for outbound efficiency.

There is one additional choice for connected inboxes. If Gmail, Outlook, or another connected account receives mail for a business address, that extra From address can either follow its domain's route or use a different saved SMTP profile just for that address.

Domain setting or one From address?

Use this rule:

For example, example.com can use Managed TrekMail SMTP for normal mail while sales@example.com, linked to a connected Gmail inbox, uses a saved Mailjet profile. Incoming messages still stay in Gmail; only outgoing delivery changes.

Configuration Steps

1. Go to Domains, pick the domain you want to configure, and open its SMTP tab.
2. Choose a route:
   • Saved SMTP profile — pick an existing profile from the dropdown if you've already added this provider to the account.
   • New custom SMTP profile — add a new provider. Enter the details below, Test the connection, then save and use it.
3. Enter the details from your provider:
   • Hostname: (e.g., email-smtp.us-east-1.amazonaws.com)
   • Port: (usually 587 for TLS)
   • Encryption: (STARTTLS / SSL/TLS)
   • Username: (API User / SMTP User)
   • Password: (API Key / SMTP Password)
4. Save the profile to apply it to this domain.

After saving, the Saved SMTP profiles section shows where the profile is used. Open the usage line to see the exact domains and sending addresses. This is useful before editing or deleting a shared profile.

Reuse it across domains

A saved profile is account-wide, so you can select it for any other domain from that domain's SMTP → Saved SMTP profile dropdown — no need to re-enter credentials. Editing a profile updates every domain that uses it.

Two account-wide controls sit under the chosen route on the SMTP tab:

• Make this the account default — new domains you add start on this route. So if you set a saved profile as the default, every new domain comes up pre-pointed at it.
• Apply to all domains — a one-time switch of every domain in the account to this route (with a confirmation prompt). Use it to move your whole account onto one provider at once.

Use a saved profile for one connected-inbox address

1. First save and test the SMTP profile under any domain's SMTP tab.
2. Open webmail and go to Settings → Sending addresses.
3. Add or edit the extra From address linked to Gmail, Outlook, or another connected inbox.
4. Open Use a different saved sending service.
5. Choose the profile and save.

If you leave that option closed, the address follows its domain's current sending settings automatically. Changing the domain route later changes how that address sends too.

See Send From a Business Address Using Gmail for the complete inbox-to-From workflow.

Provider Examples

Amazon SES

• Host: email-smtp.[region].amazonaws.com
• Port: 587 (STARTTLS)
• Username: SES SMTP Username (Not the IAM User Access Key)
• Password: SES SMTP Password (Not the IAM Secret Key)

SendGrid

• Host: smtp.sendgrid.net
• Port: 587
• Username: apikey (Literally the string "apikey")
• Password: Your actual SendGrid API Key starting with SG...

Mailgun

• Host: smtp.mailgun.org
• Port: 587
• Username: postmaster@your-domain.com
• Password: The SMTP password found in Domain Settings.

SPF & DMARC Considerations

Important: When using an external SMTP provider, your SPF record must authorize that provider — not just TrekMail. Otherwise, recipients may see SPF failures.

If you use Custom SMTP (e.g., SendGrid, Mailgun, SES):

1. Add their SPF include to your domain's SPF record. Example:

   v=spf1 include:spf.trekmail.net include:sendgrid.net -all
   

2. DKIM still signs via TrekMail unless you configure your provider's DKIM keys separately.

3. DMARC alignment: If SPF fails (because the external server isn't in your SPF), DMARC can still pass via DKIM. However, for best deliverability, ensure both SPF and DKIM align.

Recommendation: For guaranteed SPF/DMARC alignment with zero configuration, use Managed TrekMail SMTP on a paid plan. TrekMail handles all authentication automatically.

Common mistakes

• Symptom: "Connection Refused".
  • Cause: Using port 25 (often blocked). Use 587.
• Symptom: "Auth Failed" with AWS SES.
  • Cause: Using the IAM User Access Key instead of the SMTP credentials generated in the SES console. They are different.
• Symptom: SPF failures in DMARC reports.
  • Cause: Your SPF record doesn't include the external provider. Add their SPF include mechanism.
  • Note: If DKIM passes, DMARC may still pass. Check your DMARC reports for alignment details.
• Symptom: A domain's sending route changed after deleting a custom SMTP profile.
  • Cause: Profiles are reusable. Deleting one moves every affected domain to its safe fallback and moves any connected-inbox From address back to its domain's current route. On a Nano plan, a domain without another working profile cannot send until you add one or upgrade.

Before changing or deleting a profile

Open its usage details first. A single saved profile may be used by several domains and several connected-inbox From addresses.

• Editing the profile changes the connection for everything using it.
• Deleting it moves affected sending addresses back to their domain settings.
• Affected paid-plan domains fall back to the available TrekMail route; a Nano domain may stop sending until another profile is assigned.

Test the replacement route before deleting a profile used for important mail.