Top 5 Mistakes to Avoid When Writing an Email in English

Writing an email in a second language feels riskier than speaking. There is no tone of voice to soften a sentence and no chance to rephrase on the spot, so a small slip can look like a bigger problem than it is. The good news is that most email mistakes fall into a handful of predictable categories, and once you know what to check, you can catch them before you hit send.

1. Getting the tone wrong

Right off the bat, you need the right tone for your email. If you are writing to your boss, a client, or someone you have never met, you do not want to sound too casual. Email has replaced the formal business letter for the most part, but that does not mean anything goes: keep greetings professional (“Dear Mr. Smith” or “Hi Sarah” depending on the relationship), avoid slang, and match the formality of the person you are writing to. When in doubt, start more formal and let the other person set a more relaxed tone if they choose to.

2. Spelling mistakes that spell-check misses

You have a spell checker on your computer, but it will not catch every mistake. If you type “to” instead of “too,” both words are spelled correctly, so the checker stays silent while your meaning changes. The same goes for “there/their/they’re,” “your/you’re,” and “its/it’s.” These homophones are some of the most common email errors precisely because they slip past automated tools.

3. Shaky grammar

You still need proper grammar in a professional email, even a short one. If you are unsure whether a sentence is correct, read it out loud: awkward grammar usually sounds wrong before you can explain why. If you are still unsure, ask a native or fluent colleague to glance at the sentence and tell you if it sounds “right.” Two grammar points cause the most trouble in emails specifically: subject-verb agreement in long sentences, and mixing up verb tenses when describing something that already happened versus something that is still ongoing.

4. Overusing idioms

Idioms can make your writing sound natural, but only if you are certain of the meaning and the audience will understand them. “Don’t let the cat out of the bag” means “don’t reveal a secret,” and it is never meant literally. Used correctly, an idiom like this adds color; used incorrectly, or with a reader who is not a native speaker, it creates confusion instead of connection. As a rule, save idioms for informal messages to colleagues you know well, and keep formal or cross-cultural emails plain and direct.

5. Too much technical jargon

The last common mistake is packing an email with technical phrases and abbreviations the reader may not know. This makes the message harder to understand and increases the chance it gets skimmed, misread, or deleted instead of actioned. If you must use an acronym, spell it out the first time (“Key Performance Indicator (KPI)”) so every reader, regardless of their department or seniority, can follow along. Building a stronger business vocabulary also helps: the more precise your word choice, the less you need jargon as a shortcut.

A simple pre-send checklist

Before you click send, run through these five questions: Is the tone appropriate for the recipient? Have I checked the words spell-check cannot catch? Does every sentence sound right when read aloud? Will every reader understand any idioms I have used? Have I explained any jargon or acronyms? If you can answer yes to all five, your email is in good shape. If writing in English is a regular part of your job, our English Writing Course is built around exactly this kind of everyday business writing.

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