Error: SMTP Error 421
What's Causing This Error
The SMTP server may display the SMTP error 421 in many instances since this error can have numerous variations. However, it is most likely a temporary issue within the mail server or the recipient's email account.
The most common causes for this error are:
- Too many connections from your host.
- The server is busy and cannot accept the connection.
- Service is temporarily unavailable.
Solution - Here's How To Resolve It
Since these errors are mostly temporary, the user should wait for a considerable amount of time before attempting to send an email to the same server or connect to the same server.
However, in instances when the error states that there are multiple connections from or to the host, it is advisable to adhere to any limits within the email server.
Other Common SMTP Errors (and Solutions)
- SMTP Error 101
- SMTP Error 111
- SMTP Error 221
- SMTP Error 250
- SMTP Error 420
- SMTP Error 422
- SMTP Error 431
- SMTP Error 432
- SMTP Error 441
- SMTP Error 442
- SMTP Error 446
- SMTP Error 447
- SMTP Error 449
- SMTP Error 450
- SMTP Error 452
- SMTP Error 453
- SMTP Error 454
- SMTP Error 455
- SMTP Error 458
- SMTP Error 459
- SMTP Error 471
- SMTP Error 451
- SMTP Error 500
- SMTP Error 501
- SMTP Error 502
- SMTP Error 503
- SMTP Error 504
- SMTP Error 510
- SMTP Error 511
- SMTP Error 512
- SMTP Error 513
- SMTP Error 515
- SMTP Error 517
- SMTP Error 521
- SMTP Error 522
- SMTP Error 523
- SMTP Error 530
- SMTP Error 531
- SMTP Error 533
- SMTP Error 534
- SMTP Error 535
- SMTP Error 538
- SMTP Error 540
- SMTP Error 541
- SMTP Error 542
- SMTP Error 543
- SMTP Error 546
- SMTP Error 547
- SMTP Error 550
- SMTP Error 551
- SMTP Error 552
- SMTP Error 553
- SMTP Error 554
- SMTP Error 555
- SMTP Error 556
- SMTP error: data not accepted
- SMTP error from the remote mail server after end of data
- SMTP connect error 10060
- SMTP error: could not connect to SMTP host
- SMTP error port 465
- SMTP timeout error
- SMTP syntax error command unrecognized
- SMTP error: could not authenticate
- CodeIgniter SMTP Mail Not Working
- SMTP Not Working in Python
- SuddenLink SMTP Server Not Working
- SMTP Is Not Working On The Server
- SMTP Port 465 Not Working
- Moodle SMTP Error: Could Not Authenticate
- Django SMTP Sender Refused
- The SMTP server requires a secure connection 5.7.57
- SMTP error: failed to connect to server
- Error SMTP 451 4.3 5 server configuration problem
- ORA-29278: SMTP transient error: 421 service not available
- SMTP error from remote mail server
- SMTP email server error
- SMTP error from remote mail server after rcpt
- SMTP server authentication error
- An unknown error occurred connecting to the SMTP server
- SMTP error: connection to server failed
- SMTP Error Codes
View all errors
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