Issue
When submitting an HTML email to an SMTP server, you receive the following error:
501 Syntax error - line too long
This error occurs because the SMTP server enforces a maximum line length of 1000 characters for email messages, as defined by the SMTP protocol standard (RFC 5321).
Resolution
To resolve this issue, ensure that no single line in your email message exceeds the 1000-character limit. Here are several methods to handle long HTML content in your email:
Method 1: Manually Wrap Long Lines
Manually insert line breaks (\r\n or \n) in your email content to ensure no line exceeds 1000 characters. This method is tedious and impractical for large content but ensures compliance with the SMTP server's requirements.
Method 2: Automatically wrap lines
# Function to split long lines
def wrap_long_lines(content, max_length=998):
lines = content.split('\n')
wrapped_lines = []
for line in lines:
while len(line) > max_length:
wrapped_lines.append(line[:max_length])
line = line[max_length:]
wrapped_lines.append(line)
return '\n'.join(wrapped_lines)
In HTML, this can be done using a method that breaks long lines at appropriate points, to ensure it will not pass the 1000 characters or before certain tags (like <br> or <p> tags).
Here’s a basic Python example to wrap lines in an HTML email body:
import textwrap
def wrap_text(text, width):
return textwrap.fill(text, width)
# Example usage
html_body = """
<html>
<body>
<p>This is a long paragraph that needs to be wrapped to prevent long lines causing SMTP syntax errors.</p>
</body>
</html>
"""
wrapped_body = wrap_text(html_body, 998) # Wrap lines at 998 charactersExample output:
This will produce an output where long lines in the HTML content are split to ensure no line exceeds 998 characters. Here is a small excerpt of what the output might look like:
<body>
<p>This is a test email content that is intentionally made very long to demonstrate how to split long HTML lines into smaller
chunks suitable for SMTP emails. We need to ensure that no line exceeds the maximum length to avoid issues with email delivery.</p>
</body>wrapped_body = wrap_text(html_body, 998) # Wrap lines at 998 characters
Updated
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