Why are my emails being returned as undelivered?

The following are the reasons or causes for undelivered emails:

• Invalid Email Address: The recipient's email address may be incorrect, misspelled, or no longer active.
• Mailbox Full: The recipient’s mailbox is full and cannot accept new emails.
• Spam Filters: The email may have been flagged as spam by the recipient’s email server or spam filters.
• Server Issues: The recipient’s mail server may be temporarily down or experiencing technical difficulties.
• Blocked Sender: The recipient may have blocked your email address or domain.
• Attachment Size Too Large: The email contains attachments that exceed the recipient’s mail server size limits.
• DNS Issues: Problems with the Domain Name System (DNS) of either the sender’s or recipient’s email server.
• Expired Domain: The recipient's email domain has expired or is no longer active.
• Blacklisted IP Address: Your sending IP address has been flagged for spam, causing emails to be rejected.
• Authentication Issues: Missing or incorrect email authentication (SPF, DKIM, DMARC) may lead to rejection.
• Temporary Network Issues: Temporary connectivity problems between servers can result in delivery failure.
• Recipient Server Policies: The recipient’s server may have strict rules or configurations that block your email.