What the 550 message classified as spam error means #

The error typically appears like this:

550 This message was classified as SPAM and may not be delivered

In plain terms: your email didn’t pass spam checks, so it was rejected instead of being sent.
Hosting providers use outbound spam scanning to protect mail server reputation and reduce the risk of IP blacklisting.

Why this happens #

This error usually happens for one of these reasons:

• Outlook sending settings: Missing SMTP authentication can add spam-score points and trigger the block.
• Spam-like email content: Subject/body includes patterns commonly used by spammers (heavy “sales” language, too many links, odd formatting).
• Reputation/authentication problems: Poor domain authentication (SPF/DKIM/DMARC) increases the chance of filtering by policies and spam systems.

Fix #1: Enable SMTP authentication (Outlook) #

This is the #1 fix if the error happens mainly when sending from Outlook. Outbound filters commonly score Outlook messages higher
if SMTP authentication isn’t enabled.

Steps (most Outlook versions) #

1. Open Outlook → go to File.
2. Click Account Settings → Account Settings.
3. Select your email account → click Change (or Edit).
4. Click More Settings → open the Outgoing Server tab.
5. Enable: My outgoing server (SMTP) requires authentication.
6. Select: Use same settings as my incoming mail server.
7. Save and try sending again.

Fix #2: Clean up the email subject/body content #

If your outgoing mail server is using spam evaluation (even at lenient levels), the email needs to look like a normal human message.
If you’re getting blocked, review both subject and body for spam-trigger wording and formatting.

Quick content checklist #

• Remove “spammy” phrases: “FREE”, “Guaranteed”, “Act now”, “Limited time”, aggressive money terms.
• Don’t overuse ALL CAPS or excessive exclamation marks (!!!).
• Reduce links: keep to 1–2 clean links; avoid URL shorteners.
• Avoid heavy image-only emails (use text + minimal formatting).
• Keep signatures clean: no stacked banners, multiple tracking links, or copied marketing blocks.

Fast test #

1. Send a plain-text version of the same message to the same recipient.
2. If plain-text sends successfully, your HTML formatting or content is the trigger.
3. Rebuild the email with minimal formatting and retry.

Fix #3: Check SPF/DKIM/DMARC (deliverability) #

Even though this specific error is often triggered by content or SMTP-auth settings, poor authentication can increase filtering risk
and deliverability problems overall. In cPanel, the Email Deliverability feature helps you verify and publish SPF/DKIM/DMARC.

• SPF: Authorizes which servers can send on behalf of your domain. SPF is defined in RFC 7208.
• DKIM: Adds a cryptographic signature to prove the message wasn’t altered.
• DMARC: Tells receivers how to handle mail based on SPF/DKIM results (and requires valid SPF + DKIM).

Helpful official references:
cPanel Email Deliverability |
RFC 7208 (SPF) |
Google Workspace SPF guidance

What to send Hosticko Support #

If you still see the 550 message classified as spam rejection after the fixes above, send this info in your support ticket so we can pinpoint the exact rule being triggered:

• The full bounce/error message
• Your sending method (Outlook / Webmail / website form / app)
• Recipient email address and send time (with timezone)
• Email headers (if available)
• A copy of the message content (subject + body) you attempted to send

Related Hosticko guides #

• How to Obtain Email Headers (Step-by-Step)
• Connect an Email Client to a Mailbox (IMAP/SMTP)
• Correct SPF Record for Hosticko Hosting
• Email Sending Limits on Hosticko

Replace internal links with your actual Hosticko knowledgebase URLs if they differ.

FAQs #

Does this error mean my recipient marked me as spam? #

Not necessarily. This specific message commonly indicates your outbound server rejected the email after scoring it as spam-like,
before it was delivered.

Why does it happen in Outlook but not in Webmail? #

Outlook misconfiguration (especially missing SMTP authentication) can increase spam-score and trigger the block.

What if it keeps happening even with SMTP authentication enabled? #

Then the message content is usually the trigger. Simplify the subject/body, reduce links, remove promotional phrases, and test again.