Billbee & Direct Mail: 5 Automated Letter Campaigns for Multichannel Sellers — One Platform, All Channels

Multichannel sellers know the dilemma: you sell on three, five, or more platforms — Amazon, eBay, Etsy, Shopify, WooCommerce — yet on marketplaces, the customer belongs to the platform, not to you. Amazon prohibits email marketing to marketplace buyers. eBay severely restricts customer contact. You deliver the product, but the customer relationship stays with the marketplace. Billbee is where all order data from every channel converges — over 85 million orders per year, managed by more than 20,000 active users. And it is precisely this aggregated data that makes Billbee the ideal foundation for a channel that is often the only permitted way to reach marketplace customers: the physical letter.

Why Multichannel Sellers Need a Physical Channel

On Amazon, eBay, and other marketplaces, there is no direct marketing channel. The terms of service explicitly prohibit contacting marketplace customers via email or newsletter. Sellers who do so risk having their account suspended. For multichannel sellers, this creates a twofold problem: first, they cannot reach their marketplace customers. Second, communication with their own webshop customers drowns in email noise — the average professional receives 121 emails per day, and open rates have been declining steadily for years.

Physical mail solves both problems at once. It is the only permitted direct channel to customers on marketplaces, and it cuts through the digital noise with tangible presence. Temple University conducted a comprehensive study using brain scans that demonstrated printed marketing materials trigger stronger emotional responses, are remembered better, and generate higher purchase intent than digital alternatives. A letter sits on the kitchen table, not in the spam folder.

For multichannel sellers, physical mail is not a supplement — it is often the only way to build a direct customer relationship at all. The Amazon buyer who loves your product does not know your brand. The regular eBay customer has no idea you also run your own shop. A personal letter changes that.

If you want to explore the fundamental differences between direct mail and email marketing in more depth, you will find a detailed comparison in our Direct Mail vs. Email Marketing Comparison.

Billbee as the Central Data Hub for Direct Mail

Billbee is not a shop system — it is a multichannel ERP with over 120 integrations. It aggregates orders from Amazon, eBay, Etsy, Shopify, WooCommerce, PrestaShop, Gambio, and dozens of other platforms into a single customer database. For automated direct mail, this is a critical advantage: instead of setting up separate integrations for each shop, you connect one single system — and reach customers from all channels.

The Billbee automation engine operates on the principle of trigger, conditions, and actions. A trigger can be an incoming order, a status change, or a time-based event. Conditions filter by shop or channel, country, order value, payment status, or customer segment. The action is the automatic letter dispatch via AutoLetter. This combination enables highly precise campaigns that would not be possible with individual shop integrations.

For detailed information on GDPR-compliant data processing for direct mail, see our Guide to GDPR-Compliant Direct Mail. If you sell exclusively through Shopify, our Shopify Guide for Automated Direct Mail is the more relevant resource.

Campaign 1 — Post-Purchase: Brand Building with Marketplace Customers

For pure webshop sellers, the thank-you letter is a nice bonus. For multichannel sellers, it is strategically essential. On Amazon and eBay, the buyer simply does not know your brand. They "bought a product on Amazon" — not from your company. The physical letter after the first purchase is the very first real brand touchpoint. It introduces your company, builds trust, and — this is the strategic core — directs the customer to your own shop.

The trigger is simple: as soon as a first order arrives in Billbee, the automation dispatches a personalized letter. The conditions make the difference: an Amazon customer receives a different letter than a webshop customer. The marketplace buyer gets a brand introduction with a QR code leading to your own shop. The direct customer receives a classic thank-you with a cross-sell recommendation.

The strategic math is simple: if you convert 5% of your Amazon customers to direct customers, you save the marketplace commission of 10-15% on those orders. With 200 Amazon orders per month and an average cart value of 75 euros, that means: 10 converted customers x 75 euros x 15% commission = 112 euros saved monthly — from commission savings alone, on top of the regular post-purchase effect.

Campaign 2 — Cart Abandonment Recovery

70% of all shopping carts are abandoned. These customers were already ready to buy — they often just need one additional nudge. The multichannel aspect makes this campaign particularly interesting: for webshop customers, you can combine email and letter. But for marketplace customers, the email address is unavailable — Amazon and eBay do not share it with sellers. The physical letter is the only retargeting channel here to direct these customers to your own shop and encourage them to complete their purchase.

The key lies in the combination: email reaches the quick decision-makers within the first 48 hours. The letter follows 3-5 days later and wins back the customers who did not respond digitally. Billbee checks the current order status before every letter dispatch — if the customer has purchased in the meantime, the letter is automatically suppressed. This prevents unnecessary costs and irritating duplicate outreach.

Campaign 3 — Customer Reactivation: Waking Up Inactive Customers Across Channels

This is where Billbee's greatest advantage over individual shop integrations becomes clear. A Shopify store only detects inactivity within Shopify. A customer who has not ordered from the webshop in 3 months but purchased on Amazon last week would incorrectly receive a reactivation letter. Billbee prevents this: the cross-channel order history reveals true inactivity — no purchase on any channel for 60, 90, or 120 days.

This "cross-channel inactivity tracking" eliminates false-positive reactivations and focuses your budget on customers who have genuinely churned. The result: higher reactivation rates and lower cost per reactivated customer.

Cross-channel reactivation is particularly cost-efficient: because Billbee eliminates false positives, you send fewer letters while achieving a higher hit rate. A reactivated regular customer places an average of 2.4 orders in the following 12 months — the cost of the letter pays for itself with the very first follow-up order.

Campaign 4 — VIP & Upselling: Identifying Top Customers Across Channels

In every business, the Pareto principle applies: 20% of customers generate 80% of revenue. But who are your true top customers when they buy across multiple channels? A single shop report shows only a fraction of the picture. Billbee reveals the total value: 200 euros on Amazon + 150 euros on eBay + 300 euros in your own shop = a 650-euro VIP customer that no single channel would have identified as such.

The trigger is based on cross-channel total revenue: top 20% by aggregated order value across all connected shops and marketplaces. The AutoLetter integration identifies these customers automatically and dispatches personalized VIP letters that take the full customer context into account.

The results are compelling: multichannel sellers who send physical mail to their cross-channel-identified VIP customers see an average order value increase of 7-10%. Even more important is the migration effect: VIP customers who switch from the marketplace to the own shop increase the margin per order by the saved commission.

Campaign 5 — Seasonal Campaigns: Black Friday, Prime Day & Christmas

For multichannel sellers, seasonal campaigns have an additional dimension: channel-specific seasonality. Amazon Prime Day is a pure Amazon event — your eBay and webshop customers are not reached by it. The eBay holiday season has different dynamics than Black Friday on Amazon. Billbee enables segmentation by source channel and prior-year purchase behavior: Amazon customers receive the Prime Day letter, eBay buyers get the Christmas letter, and webshop customers receive the Black Friday pre-announcement.

The trigger is calendar-based, combined with Billbee's cross-channel purchase history. Customers who placed an order on Black Friday the previous year on any channel receive a personalized early-bird offer. Segmentation by source channel ensures the message matches the purchase context.

For further strategies on combining print and digital, we recommend our guide on Hybrid Marketing Strategies.

ROI Calculation: What Do Automated Letter Campaigns Deliver for Multichannel Sellers?

The decisive question: does it pay off? Let us calculate a concrete example for a typical Billbee user: a small to mid-sized multichannel seller with 800 orders per month across all channels and an average cart value of 75 euros.

For a detailed guide on ROI calculation in direct marketing, we recommend our Analytics Guide to ROI Calculation.

Best Practices: How Multichannel Sellers Get Maximum Results

The five campaigns together form a complete lifecycle marketing system via mail — cross-channel and automated. To ensure each campaign reaches its full potential, multichannel sellers should follow these eight fundamental rules.

For optimal design of your letter templates, we recommend our guide on Visual Psychology in Direct Mail Design. And for the perfect placement of your call-to-action, you will find practical instructions in our CTA Optimization Guide.

Frequently Asked Questions

Conclusion: One System, All Channels, Five Campaigns

The five automated letter campaigns together form a complete lifecycle marketing system via mail — and Billbee is the central control unit. The post-purchase letter builds your brand with marketplace customers and directs them to your own shop. The cart abandonment campaign wins back ready-to-buy webshop customers. Cross-channel reactivation targets only truly inactive customers instead of wasting budget on false positives. The VIP program identifies top customers across all channels and migrates them to the higher-margin direct channel. Seasonal campaigns leverage channel-specific purchase patterns for maximum relevance.

The crucial point: all of this runs through a single system, fully automated. After the one-time setup in Billbee, letters are triggered cross-channel, personalized, printed, and dispatched. New marketplaces are simply connected without modifying the campaign logic. For multichannel sellers who have no direct customer contact on marketplaces, physical mail is not just an additional channel — it is often the only way to build a direct customer relationship.