Enable sending from your support address

What this guide covers

Letterbook can receive forwarded mail before sending is enabled. To reply from a customer-facing address, verify that Letterbook is allowed to send on behalf of that mailbox or domain.

Setup checklist

• Choose the sending address customers should see
• Verify domain or mailbox ownership
• Configure DKIM for the sending domain
• Confirm SPF, DKIM, and DMARC alignment
• Send a test reply from Letterbook
• Check spam placement and reply threading

Configure DKIM

DKIM is the main DNS setup required before Letterbook can send trusted replies from your domain. It adds a cryptographic signature to outbound mail so receiving mail servers can verify that Letterbook is allowed to send for your domain. For background, read What is DKIM? Why do we need it?

Letterbook supports two DKIM setup paths:

• Auto configure with Domain Connect: available for Cloudflare-managed DNS.
• Manual setup: available for every other DNS provider by copying the records from Letterbook into your DNS host.

Auto configure with Cloudflare

Use auto configure when your domain's DNS is managed in Cloudflare and you have permission to update DNS records for the zone.

1. Open the sending address setup flow in Letterbook.
2. Enter the support address you want customers to see, such as support@company.com.
3. Choose the option to configure DNS automatically.
4. Select Cloudflare when prompted.
5. Sign in to Cloudflare and approve the Domain Connect request.
6. Return to Letterbook and wait for verification to finish.
7. Send a test reply from a Letterbook conversation.

Letterbook uses Domain Connect to request only the DNS records needed for sender authentication. If Cloudflare approval succeeds but verification is still pending, wait a few minutes and check again. DNS changes are usually quick in Cloudflare, but verification can still lag while mail authentication records propagate.

Manual DNS setup

Use manual setup if your DNS is not hosted in Cloudflare or if you prefer to review and add records yourself.

1. Open the sending address setup flow in Letterbook.
2. Enter the support address you want customers to see.
3. Copy each DNS record shown in Letterbook.
4. Open your DNS provider and add the records exactly as shown.
5. Save the DNS changes.
6. Return to Letterbook and click verify.
7. Send a test reply once the domain is verified.

Copy the record name, type, and value exactly. DNS providers display hostnames differently: some expect the full hostname, while others automatically append your root domain. If Letterbook asks for a record such as selector._domainkey.company.com, your DNS provider may want only selector._domainkey.

Records Letterbook may ask you to add

• DKIM records prove that Letterbook can sign mail for your domain.
• SPF records help receiving servers confirm which services can send mail for your domain.
• DMARC records tell receiving servers how to handle messages that fail authentication.

Not every domain needs every record added during setup. Letterbook will show the specific records required for your sending address.

Sending from aliases and shared mailboxes

The sending domain is the part after @. If you verify company.com, you can usually send from addresses on that domain after the address itself is allowed in Letterbook. For example, support@company.com and help@company.com share the same domain authentication.

Aliases and shared mailboxes still need to be configured carefully:

• The address should be recognizable to customers.
• The address should receive replies or forward replies back into Letterbook.
• Existing auto-replies, forwarding rules, and previous helpdesk routing should be disabled if they would create duplicate responses.

Configuration details

• Letterbook provides the DNS records needed for sender verification.
• Add the records wherever DNS is hosted for your domain.
• DNS changes can take time to propagate before verification succeeds.
• Strict DMARC policies may require exact sender alignment.
• Shared mailboxes and aliases may need both receiving and sending setup.
• You can change the default sender after another address is verified.

Troubleshooting

DNS records are still pending

Check that the record name and value match Letterbook exactly. If your DNS provider automatically appends the root domain, remove the duplicated domain from the record name.

Auto configure is not available

Auto configure currently supports Cloudflare through Domain Connect. If your domain uses another DNS provider, use manual setup.

Replies show a different sender

Confirm that the support address is selected as the default sender in Letterbook and that the domain has passed verification.

Messages go to spam

Confirm DKIM passes, check SPF and DMARC alignment, and send another test after DNS propagation finishes.

Replies create a new thread

Make sure inbound mail for the same address is forwarding into Letterbook and that another inbox or helpdesk is not also replying to the same customer thread.

The support address can receive mail but cannot send

Receiving and sending are separate setup steps. Forwarding routes inbound mail into Letterbook, while DKIM and sender verification allow Letterbook to send trusted outbound replies.