How to write an email, in one screen
Every guide gives you the same six parts. What none of them mention is that four of those parts are also read by machines before a human sees them, and that the machine reading happens first.
| From address | Decides whether the message is trusted before it is opened |
| Subject line | Read by a filter, then by a person on a lock screen |
| First line | Doubles as the preview text in the inbox list |
| Body | One request, near the top, in the active voice |
| Ending | Closing sentence with a date, then a sign-off |
| Signature | Plain text survives, images do not always |
Learning how to write an email is usually taught as a writing exercise: greeting, body, sign-off, proofread. That advice is not wrong, and it stops at the recipient’s eyes. An email is a piece of writing wrapped in a delivery system, and the delivery system reads it first.
This guide walks the message from top to bottom. For each part it gives the convention, and then what the mail system does with that part, because the two together explain why some perfectly polite messages are never answered and some are never even seen.
Before the first word: who the message is from
The From address is the first thing a recipient reads and the first thing a filter scores, and it is the one part of the message you cannot fix by rewriting.
Write from an address at a domain you control. A personal address invented for a school yearbook, a numbered free account, or a throwaway address all tell the reader how much the exchange is worth to you. There is a second effect that has nothing to do with impressions: shared role addresses such as info@ or sales@ behave differently in filtering and verification, because nobody owns them personally and complaints cannot be attributed.
The display name matters as much as the address. A reader scanning an inbox on a phone sees the name, the subject and about forty characters of preview. Those three fields are the entire decision.
The subject line
Write the subject as the conclusion, not the topic. Q3 budget approved, signature needed by Friday beats Budget, and it still works when it is the only thing visible on a lock screen.
Keep it under roughly sixty characters so it is not truncated on a narrow screen, and put the distinguishing word early: readers scan the left edge of the subject column, not the middle of it.
What reads as shouting also reads as promotional
Full capitals, stacked exclamation marks, currency amounts and a dense run of sales vocabulary annoy a human reader and are also patterns that content filters weigh. We keep a reference list of the wording that trips those filters for exactly this reason. The overlap is not a coincidence: filters were trained on what people report.
The greeting and the first line
Greet the person by name when you know it. Hi Sarah works in most workplaces, Dear Ms Okafor for a formal first contact, Dear Sir or Madam only when you genuinely could not find a name and are prepared for the message to read as a form letter.
The first line after the greeting is doing double duty. Most inbox lists show it as preview text next to the subject, so a message that opens with I hope this email finds you well spends its preview on a sentence that carries no information. Open with the reason you are writing, and treat that opening as the preview text that appears beside your subject line, because that is what it is.
The body: one request, near the top
The single most common failure in professional email is burying the request. A reader who stops after two paragraphs should already know what you want. Put the request in the first three lines, then supply the context underneath it for the reader who needs it.
Three habits carry most of the quality:
Can you approve the invoice is answerable. The invoice needs approval is a fact with nobody attached to it.Formatting is a courtesy rather than a decoration. Bold works by contrast, so a paragraph with six bold phrases has no emphasis at all. Coloured text and unusual fonts often do not survive the trip, because some clients strip styling, some invert colours in dark mode, and some readers use plain text by choice. Write so the message still works with every visual flourish removed.
Choosing the recipient fields
The three recipient fields are defined by the standard that specifies the internet message format, and clients implement those definitions literally. To names the people you expect to act, Cc names those who need to know but are not on the hook, and Bcc hides addresses from everyone else on the message.
The distinction is not stylistic. Addresses in To and Cc are visible to every recipient and travel with every forward, which is why writing to a hundred customers with their addresses in To is a disclosure rather than a typo. The full account of when each field is correct is in our explanation of what Cc and Bcc actually promise.
Attachments
Attachments are encoded before they travel. Binary files are converted with base64, which turns every three bytes into four, so a file arrives roughly a third larger than it sits on your disk. A document comfortably under a limit locally can exceed it in transit, and servers declare different maximum sizes, which is why the ceiling changes from one recipient to the next.
For anything large, send a link instead of the file. It survives every recipient’s limit, it does not consume anyone’s mailbox quota, and you can revoke it later. When you do attach, name the file the way the recipient will search for it in a year: 2026-Q3-invoice-acme.pdf beats final_v4_REAL.pdf.
Ending the message
The last sentence before your name is the highest value line in the email, because a reader who skimmed everything else will still read it. Give it a verb, an owner and a date: Can you confirm the reference by Thursday so I can release the payment run. Let me know your thoughts hands the decision about what happens next back to the person you are asking.
Then the sign-off, which carries no information and a great deal of distance. Best regards is safe almost everywhere in English business mail; Sincerely for formal or first contact; Thanks or Cheers for colleagues. Our full breakdown of sign-offs sorted by situation and the closing lines that earn a reply covers the choice in detail.
The signature block underneath is the only part of the message with a technical footprint. Keep your name, role and phone number as real text rather than baked into a graphic, because an image-only signature disappears for every recipient who blocks remote images and for every screen reader. Our guide to why HTML signatures break and what survives covers the markup side.
Before you press send
Fill in the recipient field last. Almost every half finished message that escaped did so because the address was already there when a keystroke landed in the wrong place.
Two client features are worth knowing before you need them. Most clients can hold a message until a chosen time, which is the right answer to writing at 2am, and some offer a short window to pull a message back after sending, with real limits on when that works.
The thirty second check
Does the subject state the conclusion. Is the request in the first three lines. Does the last sentence name an action and a date. Is every person in Cc there for a defensible reason. Is anything that belongs in Bcc currently in To. Is the attachment a link instead. Is the recipient field the last thing you filled in.
Writing to different readers
Writing to a company you have no contact at
Name the reason in the subject, identify yourself in the first sentence, and make the request small enough to be answered by whoever opens the shared mailbox. A message to a generic address competes with everything else in that queue, so specificity is what gets it routed to the right person rather than deleted.
Writing to a teacher or professor
Use your institutional address, put the course code in the subject, state the question in the first two sentences, and check whether the syllabus already answers it. Sign with your full name, course code and student number: a lecturer teaching four sections cannot match a first name to a roster.
Writing where the conventions differ
Register expectations vary by organisation and by market more than any guide can capture. The reliable approach is to open one notch more formal than you expect the relationship to be, then follow the other person down. Someone who replies signing with their first name has told you what to use. The wider set of conventions, and which of them are enforced by something other than habit, is in our guide to the etiquette rules and the reasons they exist.
Why a well written email still fails to arrive
Everything above assumes the message reaches the inbox. When a polite, well structured email lands in spam, the cause is almost never the writing. It is sender identity, sending history, or the shape of the message, and our breakdown of the twelve most common reasons messages are filtered works through the diagnosis in order.
The short version: authentication on your sending domain matters more than any sentence you write, a message that is mostly image with little text is a shape filters distrust, and sending to people who did not ask produces complaints that damage everything you send afterwards. Good writing cannot compensate for any of the three.
Frequently asked questions
How do I start writing my email?
Start with the subject line, not the greeting, because writing the conclusion first tells you what the message is actually about. Then greet the person by name and open with the reason you are writing. Skip I hope this email finds you well: most inbox lists show your first line as preview text, so that sentence spends your preview on nothing.
How to write a proper email example?
Subject: Invoice 4021, missing PO reference. Body: Hi Sarah, I need the PO reference for invoice 4021 before I can release Friday's payment run. The invoice is attached; everything else on it matches the order. Can you send the reference by Thursday? Then Best regards, your name and phone number. Request first, context second, deadline explicit.
What is an example of a good email?
A good email is one the reader can answer without rereading. It has a subject stating the conclusion, one request in the first three lines, context underneath for whoever needs it, a closing sentence with a date, and a signature that is readable as plain text. Length is not the measure: a three line message that gets answered is better than a page that does not.
How do I write an email on my phone?
The same rules apply, with two adjustments. Write shorter, because what feels brief on a phone keyboard often reads as curt on a desktop screen, so reread before sending. And fill in the recipient last, which matters more on a phone where an accidental tap sends immediately. Drop the automatic Sent from my phone line: it is an apology for typos you can avoid by rereading.
How do you write an email to a company?
Assume a shared mailbox with a queue. Put the specific reason in the subject, identify yourself and your account or order number in the first sentence, and make one request that whoever opens it can either answer or route. Attach evidence rather than describing it. Vague messages to generic addresses are the ones that sit longest, because nobody is sure they own them.
How do you write an email to a teacher?
Use your institutional address so the message is identifiable, put the course code and your question in the subject, and state the request in the first two sentences. Check the syllabus first and say that you did. Sign with your full name, course code and student number, and allow two business days before following up.
How do you write an email professionally?
Send from an address at a domain you control, write a subject that states the conclusion, put one request in the first three lines, keep paragraphs to four or five sentences, end with a sentence naming an action and a date, and sign off at the distance the relationship supports. Professional is mostly a matter of being easy to answer rather than of vocabulary.
How do you write an email address?
An address is a local part, an at sign, and a domain: firstname.lastname@example.com. The domain is not case sensitive. Avoid spaces, and be careful with characters that some systems handle inconsistently even where the standard allows them. When writing an address inside a message, type it as text rather than relying on a client to autolink it correctly.
About this guide
This guide walks a message from the sender field to the signature block, giving the convention for each part and what the mail system does with it. Protocol behaviour described here comes from the relevant standards, linked inline. Register and formality advice is convention rather than requirement, and is marked as such. Reviewed by the SMTPedia editorial team.
About the Author
Alaa · LinkedIn
Email infrastructure specialist with 8+ years of hands-on experience in SMTP, deliverability, and email verification. I’ve configured and troubleshot mail systems across Postfix, Exchange, and cloud relays, managed IP reputation and warmup campaigns, and built verification pipelines processing millions of addresses. My work spans DNS authentication (SPF, DKIM, DMARC, BIMI), bounce handling, blocklist monitoring, and compliance frameworks including CAN-SPAM and GDPR. I write every article on SMTPedia to give email professionals, developers, and marketers the accurate, RFC-grounded reference they need.
About SMTPedia
SMTPedia is an independent email industry reference covering SMTP, IMAP, POP3, email deliverability, marketing platforms, DNS authentication, and email verification. Every article is researched from official provider documentation, IETF RFCs, and industry best practices. Settings and configurations are verified quarterly.
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