Campaign Cleaner automatically identifies diacritic and accented characters in your email HTML and replaces them with standard ASCII equivalents - preventing rendering failures and reducing spam filter risk across all email clients.
Quick Overview of Features
Diacritic characters are letters modified by accent marks or other symbols that alter their pronunciation across various languages - examples include e, n, u, c, o, a, and hundreds of others spanning European, Slavic, and other writing systems. In email, these characters appear in subject lines, preheader text, and body copy when content is pasted from word processors, sourced from multilingual CRM records, or written by non-English speakers. Smart quotes, em-dashes, and curly apostrophes copied from word processors are related problem characters that fall into the same category.
While diacritic characters are perfectly valid in Unicode and display correctly in most modern environments when the encoding is properly declared, they become a problem when the encoding is mismatched, when content passes through legacy relay systems that handle only ASCII, or when they appear in contexts - like spam filter analysis - where their presence signals obfuscation rather than genuine multilingual content.
The most common source of rendering problems is a character encoding mismatch. If an email is declared as ASCII or Latin-1 in its headers but the body contains Unicode characters outside that range, email clients handle the conflict in different ways - some display garbled symbols, some show question marks or empty boxes, and some attempt to guess at the correct encoding with inconsistent results. The recipient sees broken text that undermines both the readability and the professional appearance of the campaign.
Older email processing infrastructure compounds the issue. Some corporate email gateways, SMTP relay systems, and archival platforms were built around ASCII assumptions and actively strip or corrupt non-ASCII bytes during transit. Subject lines are especially vulnerable because they go through a separate encoding path from the HTML body. A subject line that displays correctly in your sending platform may arrive as a string of question marks or encoded garbage in recipients using legacy mail servers, regardless of how the body of the email is handled.
Spam filters associate specific diacritic patterns with a well-documented obfuscation tactic. Spammers replace standard letters with visually similar accented characters to disguise trigger words from content-based filters - writing "frëe" instead of "free", or using lookalike Unicode characters to spell out words that would otherwise be caught immediately. Filters are trained to recognize this pattern and assign penalty points when they encounter it.
Even entirely legitimate uses of diacritics can contribute to a higher spam score when combined with other signals. An email with an accented subject line, promotional language, and a new sending domain may push past a spam threshold that a clean ASCII version of the same email would clear. Removing diacritics from subject lines and any body content where they were introduced unintentionally eliminates that risk entirely.
Older versions of Outlook, particularly those using the Word rendering engine, are the most well-documented problem clients for character encoding. Corporate environments using Exchange Server and older Lotus Notes deployments also present elevated risk. On the server side, any relay system built before Unicode became the universal email standard may silently corrupt characters during processing. Mobile clients are generally more resilient, but subject line display in push notifications can still vary across Android and iOS implementations.
The decision of whether to remove diacritics depends on your audience. For English-language campaigns, diacritics almost never appear intentionally and can be removed without any impact on meaning or readability. For campaigns targeting French, Spanish, German, Portuguese, or other audiences where accents are linguistically meaningful, the right fix is ensuring proper UTF-8 encoding rather than blanket removal. Campaign Cleaner flags diacritics and shows you each substitution so you can make an informed choice rather than applying a one-size-fits-all conversion.
Campaign Cleaner scans your entire email HTML - subject lines, preheader text, and body content - and identifies every diacritic and accented character present. It maps each character to its closest standard ASCII equivalent using a comprehensive transliteration table: é becomes e, ñ becomes n, ü becomes u, ç becomes c, and so on through the full range of common diacritic forms. The scan also catches word-processor artifacts like smart quotes, em-dashes, and curly apostrophes that would cause similar encoding problems.
The results are shown to you before any changes are applied, so you can review exactly what will be converted. You can apply the substitutions selectively or accept all of them in a single click. The cleanup runs as part of Campaign Cleaner's pre-send optimization pass, so diacritic removal happens alongside your spam score check, link analysis, and other deliverability improvements without requiring a separate workflow step.
Become a part of the Campaign Cleaner community today, and join countless satisfied customers who have witnessed significant improvements in their email deliverability and campaign success. Don’t let HTML issues hold you back; let Campaign Cleaner optimize your campaigns and boost your inbox rates.
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