Why Your Emails Go to Spam and How to Fix It

A client says they never got your proposal, then finds it in their spam folder. Sound familiar? This article explains how mail providers decide what counts as spam and what you can do to get your messages into the inbox.

How mail providers decide a message is spam

There is no single "spam switch" on the recipient's side. Their mail server scores each message on dozens of signals and adds them up. Roughly, these fall into four groups:

• Authentication — can the server confirm the message really came from a server your domain authorizes (SPF, DKIM, DMARC)?
• Reputation — how the sending IP address and your domain have behaved in the past: complaints, mail to nonexistent addresses, blocklist listings.
• Content — the text, links, attachments, and formatting.
• Recipient behavior — do people open and reply to your messages, or click "Report spam"?

No single factor guarantees inbox placement, but a serious problem in any group can push a message into spam. So check them in order, starting with authentication.

Step 1. Check SPF, DKIM, and DMARC

This is the most common cause for companies that have just moved to email on their own domain. If the records are missing or wrong, large mail providers treat your messages with suspicion, and some reject them outright.

Mechanism	What it does	Common mistake
SPF	Lists the servers allowed to send mail for your domain	Two separate SPF records instead of one; a newsletter service or website that also sends mail is left out
DKIM	Adds a cryptographic signature to each message	The public key isn't published in DNS, or the string got cut off
DMARC	Tells receivers what to do with messages that fail the checks	No record at all, or a strict policy set before all senders were verified

The easiest way to check is the message headers. Send a message to a personal Gmail or other major mailbox, open "Show original" (or "View source"), and find the Authentication-Results line. You want to see:

spf=pass smtp.mailfrom=example.uz
dkim=pass header.d=example.uz
dmarc=pass header.from=example.uz

If you see fail, softfail, or none anywhere, fix that first. Each record is covered in detail in our articles on SPF, DKIM, and DMARC. With MCMail, we set up SPF, DKIM, and DMARC for your domain and send you the exact record values when you connect.

Step 2. Check IP and domain reputation

Perfect records won't help if the server's IP address or your domain is on a blocklist. You can check for free, for example at mxtoolbox.com: enter your domain and the IP address from the Received header of your message. How to read the results and what to do if you're listed is covered in our article on blocklists.

What damages reputation:

• bulk mail to old or purchased lists — many addresses don't exist, so the server collects bounces;
• complaints from people who never asked to hear from you;
• a compromised employee mailbox used to send spam;
• a sudden jump in volume from a brand-new domain.

MCMail applies a sending rate limit. It doesn't get in the way of normal business email, but it stops a compromised mailbox from sending thousands of messages in a short time and ruining the server's reputation. That's also why mailbox security matters: strong passwords and two-factor authentication.

Step 3. Look at the content

Modern filters care less about individual "trigger words," but some habits still raise flags:

• an all-caps subject line, lots of exclamation marks, words like "urgent," "free," or "winner";
• a message that is one big image with almost no text;
• shortened links (URL shorteners) and links whose visible text doesn't match the real address;
• links to domains with a poor reputation;
• a sender name that doesn't match the address, such as "Bank" with a random address.

What helps: a clear subject, normal text, a signature with real company contact details, and links to your own domain.

Step 4. Be careful with attachments

Attachments are a common way to spread malware, so filters treat them strictly.

• Don't send executable files (.exe, .bat, .js, .scr) — they're blocked almost everywhere.
• Office documents with macros (.docm, .xlsm) often end up in spam or quarantine. If you don't need macros, save as a regular format or PDF.
• Password-protected archives can't be scanned by antivirus, so many servers treat them as suspicious.
• Send large files as a link to file storage instead of an attachment: many receiving servers limit message size.

Step 5. Keep bulk mail separate from business email

Business email is for correspondence: messages to specific people, replies to clients, documents. Bulk mail — newsletters, promotions, invitations to hundreds or thousands of addresses — is better sent through a dedicated email marketing service. Here's why:

• those services handle unsubscribes and bounces, without which bulk mail quickly damages reputation;
• if a campaign does draw complaints, your whole company's day-to-day email doesn't suffer;
• the sending rate limit on a mail server isn't designed for bulk campaigns.

If you send campaigns from your own domain, add the service to SPF and set up DKIM for it. Only email people who opted in, and include an unsubscribe link in every message.

What to do if a message already landed in spam

1. Ask the recipient to mark it "Not spam" and add your address to their contacts — that improves delivery to them right away.
2. Check the headers as described in Step 1. If a check fails, fix your DNS records.
3. Check your IP and domain against blocklists.
4. If everything looks fine but the problem keeps happening with one recipient, their own filters may be too strict. Ask their administrator to allowlist your domain.
5. If you can't find the cause, contact support at @mycloudsupport and include the headers of the problem message so we can sort it out faster.