The recipient’s email address cannot be found, or does not exist.You are sending an email using an ISP that is different to the one you are currently logged on to.Your email address has been compromised and has been blocked by recipient’s hosting server.Your IP address is blocked by the recipient’s email hosting server.For this particular error code, here are some of the possible causes: The 550 SMTP error is one of the most common error codes you may encounter. What are the causes of a 550 Blocked error? 5.1.0 - Unknown address error 550-'Mailbox is inactive'.Note: If there is a system-wide problem with the recipient's hosting server or the host is temporarily down, the following error message is also possible: 550-Verification failed for - 550-Unrouteable address - 550 Sender verify failed (in reply to RCPT TO command).Response: 550 Cyberoam Anti Spam Engine has identified this email as a spam. The attached file had the following undeliverable.
Remote host said: 550-Verification failed for (cached) callout verification failureĥ50 Sender verify failed Giving up on 240.240.240.240.
This SMTP 550 error code can be written in several different ways. Hence, the usual setup for emails is to use SMTP for outgoing emails while it is POP3 or IMAP for incoming emails.
Most often, it is used along with POP3 (Post Office Protocol 3) or IMAP (Internet Message Access Protocol) because it has limitations with regards to queueing and receiving messages. SMTP (Simple Mail Transfer Protocol) is a set of standardised rules on sending and receiving emails (electronic mails). Note: This error is often a problem at the recipient’s end, meaning it is probably not caused by your own email hosting server.