A business email is not just composed of words, but of empty space. The space between paragraphs lets the recipient see where one idea stops and another one starts. Without that space, even a friendly message with a direct ask could become more onerous than it has to be.
Examine one of your recently written email drafts and you will probably notice where the reader is likely to take a breath. The salutation is one idea. The purpose of the message is another. There may be a distinct line for the request, a separate line for information on an attachment, another for the deadline, and another for a concluding phrase. If all of that is contained within a single large paragraph, the recipient must separate those ideas themselves mentally as they read. You risk your reader missing the most important element you wanted them to do.
A long paragraph is often unintentional: the writer tries to be helpful and informative, then ends up including background, description, information about an attachment, ask, deadline and sign-off all within a single block. It is not a bad thing to want to include all of that information, but it can become overwhelming. When working on professional communication the recipient is usually only looking for a specific goal, task or outcome. A single long paragraph can hide those elements and make them impossible to find.
You can fix a congested draft by giving each paragraph its own specific assignment. For example, the first brief paragraph can state the topic of your message. The second can state the primary piece of information, or ask. The third can include a deadline, note about an attachment, or expectation of a response. And a sign off may need its own separate line. That does not make your writing look childlike or over-simplified; rather, it makes it easier to scan for information.
An extra paragraph break before a request is also helpful. If you ask someone to do something within your first three sentences, the recipient may overlook it or fail to respond quickly enough. The request sentence may look something like this: “Can you please review the attached draft by Thursday?” Making the task a sentence of its own gives it extra visibility. The same applies to a deadline: make sure the date stands out instead of being lost within a paragraph of additional information.
Paragraph breaks can also affect tone. If your message looks cluttered, it may also sound hurried, even with a polite word choice. More empty space can make a follow-up email, explanation or update more calm in appearance and effect. The recipient also gets a clear map for reading the email: context to first, task second, additional detail third, closing line fourth. The message becomes more likely to be acted upon because the structure itself suggests the main points.
Before you check the spelling of a business email or review it for tone, review the layout of the document. Does it contain a big block of writing? Is the request easy to locate? Does the deadline or reference to an attachment appear immediately? If not, break the long paragraph into multiple short ones before you edit. Just be careful you do not give each sentence its own paragraph and make the document feel disjointed. You just want enough empty space so your audience can move easily through your text.