SMTP error 517 represents a permanent or "5xx" error message issued by a mail server, indicating the sender's email address is barred or deactivated due to policy breaches or related reasons. This error signifies the mail server's refusal to accept or dispatch emails originating from the sender, presenting a constraining setback.

What are the cases covered in SMTP Error 517?

1. Case 1: "517 5.2.2 mailbox@example.com: Mailbox full. Please try again later."
2. Case 2: "517 4.3.1 mailbox@example.com: Over quota. Cannot receive further messages at this time."
3. Case 3: "517 5.2.2 mailbox@example.com: The recipient's mailbox is currently full. Delivery temporarily suspended."
4. Case 4: "517 4.7.1 mailbox@example.com: Delivery not authorized, message refused. Recipient mailbox quota exceeded."

What’s Causing This SMTP Error 517 In Your Servers? 

SMTP error 517 commonly arises due to one or more of the following factors:

1. Policy Violations: The sender's email address might be flagged for spamming, engaging in abusive conduct, or breaching the recipient server's regulations.
2. Blacklisting: The sender's domain or IP address could be enlisted in email blacklists, which are maintained to obstruct known origins of spam or malicious emails.‍
3. Suspected Phishing or Fraud: The sender's email address or its content might arouse suspicions of phishing endeavors, fraudulent activities, or other malevolent actions.
4. Recipient Server's Security Measures: The recipient's email server might enforce stringent security protocols triggering SMTP error 517 for specific senders.

Remediating SMTP error 517

1. To tackle SMTP error 517 occurring in PHPMailer or Jenkins, validating Active Directory attributes is essential.
2. Confirm that all affected users have a properly configured mail attribute within Active Directory.
3. Ensure that no erroneous characters are present in the mail attribute, which could lead to SMTP error 517.
4. This validation process is crucial for maintaining the integrity of email delivery mechanisms in PHPMailer and Jenkins setups.

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