Email Delivery Best Practices
Discover essential tips for crafting compelling email subject lines and engaging content to boost open rates and enhance communication.
Table of Contents
Best Practices for Email Delivery: Subject Lines and Message Content
Biller Genie automatically generates email subject lines and message content that follow industry best practices for reliable delivery across major email providers.
While these fields are editable, changing subject lines or message content incorrectly can increase the likelihood that emails are routed to junk or spam folders by email services such as Google Workspace, Microsoft 365, and other corporate email platforms.
This article outlines best practices to help ensure the highest possible email delivery rate when customizing invoice-related emails.
WARNING!
Changing subject lines or message content in ways that resemble marketing, promotional, or automated bulk emails can negatively impact email delivery.
Email providers analyze subject lines and body content to determine whether a message should be delivered to the inbox, junk folder, or blocked entirely.
How Biller Genie Email Templates Work
Biller Genie includes multiple automated email templates that are triggered based on invoice activity and timing.
These templates can be found in the Biller Genie portal under:
Add-Ons > Invoice Messenger
Add-Ons > Reminders
Each template includes editable fields such as the header, subject line, and message body.
Available Email Templates
The most commonly used templates include:
New Invoice
Automatically sent when a new invoice is created
Paid Invoice
Automatically sent once an invoice is marked as paid
Invoice
Manually sent by a merchant (for example, when sending an invoice directly from the portal)
Invoice Reminders
Automatically sent based on reminder schedules and rules
(Configured under Add-Ons > Reminders)
New Invoice, Paid Invoice, and Invoice Reminders are system-triggered based on invoice activity and reminder rules. The Invoice template is merchant-initiated and sent manually. While merchants can customize the content of any template, the sending behavior depends on the template type.
Subject Line Best Practices
Biller Genie prepopulates subject lines using proven patterns that email providers recognize as transactional and legitimate.
When modifying subject lines, follow the guidelines below.
Recommended Practices:
- Keep subject lines short, clear, and invoice-focused
- Include invoice identifiers such as invoice numbers
- Reference your business name using merge fields
- Use neutral, transactional language
Examples of recommended subject line formats include:
- Invoice #{InvoiceNumber} from {DBAName}
- New Invoice: #{InvoiceNumber}
- Paid: Invoice #{InvoiceNumber}
What to Avoid in Subject Lines
Avoid subject lines that resemble marketing or promotional emails, including:
- Excessive punctuation (!!!, ???)
- ALL CAPS wording
- Emojis or symbols
- Urgent or sales-driven language
Examples to avoid:
- “PAY NOW!!!”
- “FINAL NOTICE – ACT FAST”
- “LIMITED TIME OFFER”
- “You must open this email immediately”
These patterns are commonly flagged by spam filters and can reduce deliverability.
Message Body Best Practices
Email providers also analyze message content when determining whether an email is delivered to the inbox or routed to junk folders.
Recommended Practices
- Keep messages professional and invoice-focused
- Use clear spacing and readable formatting
- Avoid excessive links or external URLs
- Use standard punctuation and capitalization
- Limit repeated keywords related to payment urgency
What to Avoid in Message Content
Avoid adding content that may be interpreted as promotional or automated bulk messaging, including:
- Marketing or upsell language
- Large blocks of bold or colored text
- Excessive urgency or threatening language
- Repeated calls to action beyond the payment link
Why Prepopulated Templates Are Recommended
Biller Genie’s default subject lines and message content are designed to:
- Align with transactional email best practices
- Pass common spam-filter and reputation checks
- Deliver consistently across major email providers
- Reduce false positives in junk and spam filtering systems
While customization is supported, we strongly recommend keeping changes minimal and aligned with the original structure.
Confirming Successful Email Delivery
After making changes to subject lines or message content:
- Send a test invoice to yourself
- Verify delivery to your inbox (not junk or spam)
- Confirm that customers receive invoices promptly
- Verify that reminder and paid invoice emails are delivered as expected
If emails are routed to junk folders after changes, revert to the original subject line or message structure.
Still Seeing Delivery Problems?
If email delivery problems persist after following these best practices, refer to Email Delivery Troubleshooting to review your email security configuration and ensure that Biller Genie sending IPs are allowlisted.
You may also contact Biller Genie support at support@billergenie.com and include:
Which email template was modified
The subject line and message content used
The email provider involved
Our support team is happy to help review configuration and delivery behavior.