What's Causing This Error
SMTP error 551 occurs when an email bounces during the delivery process. Two types of bounces may take place:
- Soft Bounce - Soft bounce takes place when the recipient's mailbox is full or if their email server is temporarily unavailable
- Hard Bounce - Hard bounce occurs when the email address is invalid or if the mail server attempts to deliver the email to another server that does not handle the recipient's email address.
The reason behind this error code may not always be clear and other reasons can also contribute to causing an email to bounce.
Solution - Here's How To Resolve It
To resolve this error, ensure no underlying issues affect the email server or the connectivity.
The following common troubleshooting steps can help narrow down and resolve the issue at hand:
- Ensure that all recipient's email addresses are valid.
- Ensure that the recipient has enough space in their mailbox to receive the email.
- Ensure that the recipient's email server is available and is accepting email.
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 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
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- Django SMTP Sender Refused
- The SMTP server requires a secure connection 5.7.57
- SMTP Error Codes
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