Does using base64 vs UTF-8 HTML/Text impact email deliverability?

Email marketer from Sendinblue recommends keeping HTML email designs simple and using inline CSS for better compatibility across email clients. Avoid complex or unusual HTML structures, which could inadvertently trigger spam filters. Clean, well-formatted HTML is preferable for deliverability.

Email marketer from Reddit shares that excessively encoding an email message may make it appear suspicious. Suggests that it can trigger spam filters if the encoding is seen as an attempt to hide the content.

Email marketer from Mailjet shares that using clean HTML code, avoiding excessive use of images without alt text, and maintaining a good sender reputation are key deliverability factors. While not directly mentioning base64, impliedly avoid complex or unusual encoding of HTML which could negatively impact the rendering or perception of the email.

Email marketer from Stack Overflow explains that base64 encoding increases message size by approximately 33%, which can be significant for large attachments or complex emails. Increased size can contribute to deliverability issues if it causes emails to be rejected by servers with size limits or if it negatively impacts sender reputation due to increased bandwidth usage. Using UTF-8 and specifying the correct character set is generally preferable for text content.

Email marketer from HubSpot stresses the importance of a good sender reputation. If your emails are flagged as spam, the ESPs will automatically move your future emails to the spam folder, regardless of the encoding used. You can avoid this by warming up your IP address, cleaning up your contact list, and authenticating your emails.

Email marketer from EmailToolTester recommends using email testing tools to check how your emails render across different email clients and whether they trigger spam filters. These tools can help identify issues related to encoding, HTML structure, or content that might affect deliverability. The tool will help you confirm if you have implemented the encodings and HTML correctly.

Email marketer from Litmus shares that proper HTML coding is important. Improperly formatted or excessively complex HTML can trigger spam filters. Litmus recommends using well-formed HTML and avoiding techniques that are commonly associated with spam, such as obfuscated code.

Email marketer from Reddit emphasizes the importance of using a proper email setup (SPF, DKIM, DMARC) as a prerequisite for any encoding considerations. Shares that focusing on authentication is generally more impactful than specific encoding choices for deliverability.

Email marketer from Constant Contact recommends avoiding spam trigger words in your email content and subject line. Spam trigger words may cause email provider spam filters to flag your email as spam, which would affect your deliverability rate.

Expert from Spam Resource shares that email filters look at a variety of things but in general if you are encoding things that should not be encoded that it will likely be flagged negatively by spam filters. If you base64 encode text that should not be encoded you will negatively impact your deliverability.

Expert from Email Geeks explains that there was a time when base64 encoding plain text was assigned negative reputation due to spammers using it to bypass early content filters. Filters started cracking the Base64 encoding. Recommends Quoted Printable encoding if high ASCII is needed.

Expert from Word to the Wise explains that quoted-printable is the preferred encoding for text, particularly if the character set is not ASCII, and recommends using it unless there is a specific reason to use base64. Shares that base64 is more appropriate for binary content. Properly declaring the character set is also essential.

Expert from Email Geeks shares that it's bad practice to base64 encode something that is text, use quoted-printable encoding.

Expert from Email Geeks shares that while base64 and quoted-printable do the same thing at a high level, quoted-printable is better for text content because it's more readable and smaller, while base64 is better for non-western text content where readability doesn't matter and base64 is smaller. Also indicates that, in 2020, these encoding choices don't directly affect deliverability, but using quoted-printable makes it easier for humans reviewing the email to see that no shenanigans are being attempted, which can help if you're in a situation where someone is looking at your mail to make a human decision about it.

Expert from Email Geeks simplifies the advice to "Always use quoted-printable for anything that looks vaguely like ascii text". Explains that utf8 is a character encoding to describe glyphs via bytes, like utf16, ascii, etc., while Base64 and quoted-printable "armor" byte streams for email transmission by converting them to 7-bit ascii characters. You always need both a character encoding and a content-transfer encoding.

Documentation from Google shares that authenticating your email with SPF, DKIM, and DMARC is crucial for deliverability to Gmail users. A strong authentication setup improves trust and prevents your emails from being marked as spam. Ensure your domain meets Google's email authentication standards.

Documentation from MDN explains that UTF-8 is a dominant character encoding for the web and email. Using UTF-8 ensures broad compatibility and correct display of text across different systems. Improper handling of UTF-8 can lead to garbled text, which might affect deliverability if it makes the email appear unprofessional or suspicious.

Documentation from Microsoft shares that choosing the correct character encoding is critical for displaying text correctly. Using incorrect character encodings can lead to mojibake (garbled text), which may negatively impact the user experience and potentially affect deliverability if the content becomes unreadable or suspicious.

Documentation from IETF explains that content-transfer-encodings (like base64 and quoted-printable) are used to represent arbitrary binary data in a format suitable for transport over email. The choice of encoding depends on the nature of the data being transmitted. Base64 is designed for binary data, while quoted-printable is intended for mostly text data.

Documentation from Oracle explains that character sets used in mail headers must be encoded according to RFC 2047, especially when using non-ASCII characters. Failure to properly encode these headers can lead to display issues and potentially trigger spam filters. UTF-8 is often recommended but needs correct implementation.