Yahoo have extremely strict criteria for accepting email and often defer e-mail if they think that it might be spam or if they are busy - they call this 'de-prioritising email'. Unfortunately their system often defers perfectly acceptable email. Yahoo also run the e-mail system for BT so you may get the message sending to BT email addresses too.
A "451 Message temporarily deferred" error typically indicates that the recipient's mail server is temporarily unable to accept incoming messages. This could be due to various reasons such as:
- Temporary server issues: The recipient's mail server might be experiencing technical difficulties, such as high load, maintenance, or configuration problems.
- Volume control: The recipient's mail server might have implemented rate limiting or volume control measures to prevent spam or overload. This means that if you're sending a large volume of emails in a short period, some messages may be temporarily deferred.
- Policy-based filtering: The recipient's mail server might have policies in place that temporarily defer messages based on certain criteria, such as suspicion of spam, virus scanning, or other security checks.
- Greylisting: Some mail servers employ a technique called greylisting, which temporarily defers emails from unknown or unrecognised senders. The server will typically accept the email upon a retry from the sending server after a certain period.
If you're consistently receiving this error when sending emails to Yahoo or BT addresses, it's advisable to wait for some time and try sending the email again later. If the issue persists, you may want to contact the recipient's email provider for further assistance or consider alternative means of contacting the recipient.
