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ProtocolCodes
452
SMTP

452 Insufficient Storage

The requested action was not taken because the server has insufficient system storage. The server cannot accept more mail until storage is freed.

On this page

When You See This Code

When the mail server's disk is full or the recipient's mailbox has exceeded its storage quota. The server cannot store additional messages.

How to Fix

If you are the sender, retry later after the recipient frees up space. If you manage the server, clear disk space, increase quotas, or archive old messages.

Specification

View RFC / Specification →

Compare With

211 System Status 214 Help Message 220 Service Ready 221 Closing Connection 235 Authentication Successful 250 OK 251 User Not Local 252 Cannot Verify User 334 Server Challenge 354 Start Mail Input 421 Service Not Available 450 Mailbox Unavailable

Guides

Debugging SMTP Delivery Failures: 4xx Temporary vs 5xx Permanent Debugging & Troubleshooting
SMTP Reply Codes: What Your Email Server Is Telling You Email Delivery
Improving Email Deliverability: SPF, DKIM, and DMARC Setup Email Delivery
Diagnosing Email Bounces: Soft (4xx) vs Hard (5xx) Email Delivery
SMTP Authentication Methods Explained Email Delivery
Email Header Analysis: Tracing Delivery Path Email Delivery
Bulk Email Delivery: Avoiding the Spam Folder Email Delivery
DMARC Reporting: Analyzing Aggregate and Forensic Reports Email Delivery
IP Warming for Email: Building Sender Reputation from Scratch Email Delivery
Email Feedback Loops (FBL): Processing Spam Complaints Email Delivery
Transactional Email Best Practices: Receipts, Alerts, and Password Resets Email Delivery
DNS Record Types Explained: A, AAAA, CNAME, MX, TXT, and Beyond DNS & Networking
TCP Three-Way Handshake and Connection Lifecycle DNS & Networking
RFC 5321: SMTP Protocol Deep Dive Protocol Deep Dives
RFC 959: FTP Protocol Deep Dive Protocol Deep Dives
TLS 1.3: Faster, Simpler, More Secure Protocol Deep Dives

Debugging Scenarios

452 Insufficient Storage — Mailbox Full Beginner

Glossary

Status Code Media Type (MIME Type) TLS Handshake TLS Certificate (SSL Certificate) Cipher Suite Authentication TCP/IP Three-Way Handshake Port Number Firewall IPv6 Exponential Backoff Error Code Mapping Poison Message Request-Response Model RFC (Request for Comments) IANA (Internet Assigned Numbers Authority) Message Framing Connection-Oriented Text vs Binary Protocol MX Record PTR Record SMTP Relay SPF, DKIM, and DMARC Bounce Rate (Email) Email Deliverability MTA (Mail Transfer Agent) SMTP Pipelining Greylisting Backscatter Envelope vs Header STARTTLS SMTP Authentication (SMTP AUTH) Open Relay Email Queue MIME Multipart ARC (Authenticated Received Chain) BIMI (Brand Indicators for Message Identification) DSN (Delivery Status Notification) Email Header Injection SMTP Enhanced Status Codes MDN (Message Disposition Notification) MIME Type TLS Versions TLS 1.3 Certificate Authority (CA) Forward Secrecy (PFS) SNI (Server Name Indication) TLS Session Resumption Key Exchange PKI (Public Key Infrastructure)

Frequently Asked Questions

What is SMTP 452 Insufficient Storage?

The requested action was not taken because the server has insufficient system storage. The server cannot accept more mail until storage is freed.

When do you see SMTP 452 Insufficient Storage?

When the mail server's disk is full or the recipient's mailbox has exceeded its storage quota. The server cannot store additional messages.

How to fix SMTP 452 Insufficient Storage?

If you are the sender, retry later after the recipient frees up space. If you manage the server, clear disk space, increase quotas, or archive old messages.