SMTP Error (503) / SPF & DKIM Validation Failures

Troubleshooting: SMTP Error (503) – SPF & DKIM Validation

If you can receive email but encounter the error "SMTP Error (503): Failed to set sender... (5.3.2 Cannot send mail: check SPF or DKIM records)" when sending, it means your domain is not fully configured and saved within Purelymail. This error occurs because our sending server cannot yet verify that your domain has permission to deliver mail through our system.

1. Save After Checking

A huge callout for all users is that the Check DNS Records only verifies that your records exist on the internet; it does not automatically apply them to your account.

• Go to the Domains section of your Purelymail Account Admin portal and select the domain you are setting up.

• Even if the DNS Check shows a green "Pass," you must click SAVE.

• Why: Clicking Save is the only way to commit these records internally. Without this step, our SMTP server will continue to block outgoing mail to prevent unauthorized sending. This accounts for roughly 50% of all setup issues!

2. Eliminate Duplicate SPF Records

You are strictly restricted to one SPF record per domain. If you have multiple TXT records starting with v=spf1, your DNS configuration is invalid.

• If Purelymail is your only provider: Use our defined SPF record:

  v=spf1 include:_spf.purelymail.com ~all

• If you use multiple providers: You must combine them into a single record. For example, if you already use Example, your record could look like this:

  v=spf1 include:_spf.example.com include:_spf.purelymail.com ~all

The Fix: Search your DNS settings for any existing v=spf1 records and either replace them or merge them. Never create a second SPF record.

3. Correcting DKIM Host Records

A common cause of the "5.3.2" error is a formatting mistake in the DKIM Host field within your DNS provider (like Namecheap).

• The Error: Adding the full value or extra underscores into the Host field (e.g., entering purelymail1._domainkey.example.comas the Host).

• The Fix:

  • Type: CNAME Record

  • Host: purelymail1._domainkey

  • Value: key1.dkimroot.purelymail.com.

• Note: Most registrars automatically append your domain name. Ensure you have not entered your full domain name into the Host field, or the record will fail.

• All Records: Make sure to set all 3 DKIM records provided in the Domain setup section of Purelymail Account Admin portal.

4. Use the Correct Host Symbol

For SPF and MX records, your registrar requires a specific "Host" or "Name" value to point to your root domain.

• Namecheap / Cloudflare: Use the @ symbol in the Host field.

• Other Registrars: Some require you to leave the Host field blank.

• Propagation: After clicking Save in the Purelymail portal, allow up to 1 hour for the changes to update globally.

5. Last Resort: Open a Support Ticket

If you have confirmed your records are formatted correctly, passed the DNS check, and clicked Save, but you still receive the 503 error after one hour, please open a support ticket.

Include the following in your ticket for a faster resolution:

1.   Your Purelymail Account Admin user

2. A full screenshot of your DNS records as they appear at your registrar (e.g., Namecheap).

3. The specific domain(s) experiencing the issue.

4. Confirmation that you have clicked the Save button in the Domains section after your records passed the check.