Do you want to send an attachment with your marketing or automated emails but haven’t found clear guidance? This article will answer all your questions about sending email attachments, especially in transactional emails.
While email attachments do have technical limitations, a smart approach can significantly enhance the relevance and value of your emails. Discover how to leverage attachments effectively to engage your audience and streamline your communication workflows.
4 Benefits of Attachments in Transactional Emails
Transactional emails are direct responses to a recipient’s action, such as a password reset or an order confirmation. These emails are crucial for informing customers and strengthening their bond with your brand. Attachments, when used correctly, can amplify this effect. They empower your recipients to:
- Save content for future reference;
- Import data into other systems, particularly in .csv or .xml formats;
- Edit, view, or sign files directly;
- Easily share files with others.
Among the many file types, PDF stands out. Let’s explore why.
Why PDF Format is Preferred for Attachments
Attachments come in various forms, but popular choices include Office documents (.docx, .xlsx), HTML, calendar items (.ical), and PDFs. While hundreds of file extensions exist, most are unsuitable for email attachments. The PDF format, however, offers distinct advantages, making it the de facto standard for email attachments:
PDF attachments:
- Are readable and zoomable on any device;
- Allow for interactivity within the document;
- Maintain consistent formatting, fonts, images, and margins across all platforms;
- Can be saved in various aspect ratios.
The portability of the PDF format ensures that it looks identical regardless of the device or system used to view it. This consistency, from Google Drive to iCloud or your business systems to a recipient’s inbox, is unparalleled. It’s the only format that guarantees both sender and receiver view the file exactly the same way, even in an inbox preview.
Indirect Attachment Sending with a Link
Due to attachment size limits—often quickly exceeding 20MB—it’s sometimes more practical to link to a file’s location rather than attaching it directly. This method allows recipients to retrieve the PDF, a common practice for whitepapers or large documents.
Sending attachments indirectly via a link is also advisable when the file contains personal information, requires signing with external software, or is not in PDF format. You can host documents within their creation software (e.g., your accounting package), on your website (e.g., a landing page), a Content Delivery Network (CDN), or a document hosting service like Google Drive, Dropbox, OneDrive, or a specialized Document Management Solution (DMS) or Digital Asset Management (DAM) system.
When You Should NOT Send Attachments
Sending PDF attachments with your marketing emails often causes more harm than good. It can indirectly damage your email deliverability, and many Email Marketing providers restrict sending mass emails with attachments.
Therefore, reserve attachments primarily for transactional emails, never for marketing campaigns. Even with transactional emails, certain situations warrant avoiding PDF attachments. Do not add PDF files to transactional emails such as:
- Welcome emails;
- Password reset emails;
- Two-factor authentication emails;
- Notification emails.
In summary: Avoid attaching files to emails designed solely to inform the recipient or prompt a simple action, like clicking a password reset button. Such attachments can be confusing and clutter their inbox unnecessarily.
Six Use Cases for PDF Attachments in Email
You might be wondering where PDF attachments are appropriate. Here are several best practices for emails with attachments:
- Standardized PDF attachments;
- Payment information;
- Order confirmations;
- Digital tickets;
- Periodic reports;
- Digital signatures and forms.
1. Standardized PDF Attachments
Most PDFs sent via email are created once and stored in your CMS or the cloud. You’ll find numerous examples in both B2B and B2C emails:
- Whitepapers;
- Presentations;
- eBooks;
- Floor plans;
- Price lists;
- Directions.
Some attach these files directly, while others link to their online location. Regardless, these attachments are typically non-interactive and optimized for printing.
2. Payment Information and Invoices
Other frequently used PDF files include invoices, receipts, and quotes. These all contain financial information. Since most customers will print or save these PDFs for administrative purposes, you can send them as simple PDF files.
Invoices must appear legitimate (and be so), so include your logo, company details, etc., to instill confidence in your recipient. This information is not only legally required but also helpful for recipients to confirm their data or upload directly into accounting software. However, never include data sensitive to phishing, such as full credit card numbers. Instead of “5115 5477 8866 3418,” hash it to “XXXX XXXX XXXX X418.”
3. Order Confirmations
eCommerce marketers know that order confirmations are among the most opened and clicked emails. They reassure customers that their order was received correctly and make it easy to retrieve order information without logging in again.
Unlike invoices, order confirmation PDFs are excellent for featuring product images, as they serve a different purpose. By enriching your order confirmations with all the details your recipient needs, you increase engagement with your email and save valuable customer service calls.
4. Include Digital Tickets in Your Emails
Some more advanced PDFs combine data from multiple source systems. A good example is a digital ticket. This type of PDF often includes a QR code, event information, payment details, and order data. This information is typically stored in various locations and must be retrieved from there.
5. Send PDF Reports
Many B2B and B2C companies provide periodic reports to their customers. Examples include annual “Your favorite songs of last year,” monthly “Check your progress in May,” or even daily “These are the market changes today.” These reports cluster a lot of data.
Statistics are often linked to specific users and require personalized content. Imagine you are learning a new language, and your monthly reports include the number of courses you’ve taken and the progress you’ve made. The remaining content varies: either you’re doing great, or you need to put in more effort. Another well-known example is the monthly email sent by energy providers to help customers understand their energy consumption.
6. Digital Signatures & Forms
The PDF format offers other interesting features, such as:
- Encryption;
- Digital signatures;
- Metadata.
Senders can create advanced workflows using digital signatures, which are useful when contracts are part of automated processes.
Because PDFs can be encrypted, they offer a secure and convenient way to share data. Recipients can simply fill out the PDF, reply to the email, and trust that their data will be processed securely.
External vs. Dynamic: How to Generate PDF Attachments?
There are two primary methods for adding attachments to emails: through a trigger (externally rendered) or dynamically during the email delivery process.
What are Externally Generated Attachments?
As the name suggests, this type of attachment is pre-generated and hosted somewhere your email platform can access it. It might be created by a Digital Asset Management (DAM) tool or a dedicated PDF generation tool.
You then configure how this PDF is sent with the email. If your accounting software generates both the email and the PDF, everything can be sent via the SMTP protocol. If you use separate tools, your email platform can combine them via an API call.
What are Dynamically Generated Attachments?
Dynamically generated PDFs are created on demand. You use a PDF template and populate it with necessary variables, much like a transactional email. The structure is in place, and the data is added the moment it’s ready to be sent!
This method allows you to pull more data from your source systems, ensuring the PDF is always up-to-date and reflects your brand’s style. Providers like Flowmailer generate your transactional emails (and their attachments) as needed.
When to Send Which Type of PDF?
In the email delivery process, externally generated, static attachments are the easiest solution. You generate them once and send them as an attachment via SMTP. However, you might lack control over the design and personalization of such PDFs, leading to generic attachments.
Dynamic attachments excel when multiple data points need to be merged or when an attachment requires hyper-personalization. Invoices, access tickets, and periodic reports are perfect candidates for dynamic generation. While dynamic PDF generation can be more complex due to technical details in XHTML (more on this later), the benefits often outweigh the challenges.
Ask yourself the following questions when considering which type of attachment to send:
- Does my attachment need to be interactive or highly engaging?
- Do I need data from multiple source systems to create the PDF?
- Do I want control over the design of my PDFs?
If the answer to two or three of these questions is “yes,” it makes more sense to generate your PDFs dynamically. In some cases, you can use both externally generated and dynamic attachments in the same email, as shown in this example from Beekse Bergen:
How to Create Effective, Dynamic Email Attachments
To begin creating dynamic attachments, you’ll need a specialized platform. While tools like accounting software can generate PDFs, their capabilities are often limited. For full control, it’s advisable to use an advanced Email API or a dedicated PDF generation platform.
1. Data Collection
Customer information today extends beyond personal connections. Every business uses various systems to gather data about their customers—what they like, what they do, what they buy. This information is invaluable for personalizing your communications.
Each system holds specific customer data; your billing system doesn’t have the same information as your social media hub, and vice versa. However, you might want to use different pieces of customer information in your emails or PDFs. A Customer Data Platform (CDP) can collect, centralize, and make this data available.
To create PDFs with various pieces of information, you need to leverage APIs. APIs allow you to quickly retrieve data from multiple sources and use it to add variables to your emails and attachments. You can then seamlessly process these variables in an XHTML template.
2. Personalize Content
Once you have gathered the necessary data, you can personalize the content of your PDF. Variables allow your PDFs to be unique for each recipient. For instance, if you offer both direct debit and deferred payment options, you can add a QR code for deferred payments while omitting it for direct debits.
3. Create XHTML and Convert to PDF
Unlike email templates (HTML/CSS), PDF templates are in XHTML format. This allows you to use virtually the same variables as in email templates, but it also comes with some limitations. For example, XHTML and CSS don’t always cooperate perfectly, and managing margins can be trickier in XHTML.
While this article isn’t a comprehensive guide to XHTML development, for more information, you can refer to the O’Reilly website.
Choosing a Provider for Sending PDF Attachments
Now that you understand how to add PDF files, let’s look at which email providers support them. Any SMTP relay can technically deliver externally generated attachments. However, many Email Marketing Providers lack the functionality to create dynamic PDFs. The table below illustrates attachment support across different types of providers:
Most email marketing platforms do not allow attachments at all. If they do, they often prefer you host files on services like Dropbox and provide a link. To generate your invoices and tickets, you’ll need a different platform. Since cloud storage isn’t designed for PDF generation, consider dedicated PDF generation tools like PDFMonkey, ContractExpress, Avodocs, and DocSpring.