What's Causing This Error
This error occurs when due to authentication problems with the SMTP server.
Solution - Here's How To Resolve It
Ensure that you are providing the correct username and password for authentication. Additionally, ensure that you connect to the correct port based on SSL or TLS.
Please note that if you connect to the Google SMTP servers, enable "Less Secure Sign-In" for the sender account.
Other Common SMTP Errors (and Solutions)
- SMTP Error 101
- SMTP Error 111
- SMTP Error 221
- SMTP Error 250
- SMTP Error 420
- SMTP Error 421
- 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
- 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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