How to Fix “550 Permanent failure for one or more recipients” SMTP error?

We have received lots of requests from our clients regarding the “550 permanent failure for one or more recipients error”. This is an SMTP (Simple Mail Transfer Protocol) error and this error mainly occurs when the sending mail gets blocked by the receiving mail hosting server.

What causes 550 permanent SMTP errors?

  1. The IP address of the sender’s server is blacklisted in the receiver’s mail hosting server.
  2. The email address of the recipient does not exist or is not found.
  3. In case of the recipient’s mail inbox is full and there is not enough space to receive any more mails.
  4. The recipient’s email is temporarily blocked.
  5. The recipient’s hosting server considers your mails are spam and hence the mail gets blocked.

How to fix 550 permanent SMTP errors?

  • Sender’s server IP blacklisted in receiver’s mail hosting server:

If your server is sending spam frequently or any phishing emails, then the IP of your server will block on the recipient server firewall. Also nowadays there are many kinds of spam filtering tools, they will filter spam-sending IPs or domains.

You can check if your IP address is blacklisted using many tools which are available nowadays. For example, you can use the MX toolbox tool for checking IP or domain blacklist.

If you are using a shared server there is the chance of sending spam from other domains that are hosted on your same server, so hence the IP address of the server will get blacklisted.

If you are using a dedicated server without a firewall or improper firewall configuration there is a chance of VPS getting hacked.

  • Bad SPF Record for the domain

An SPF (Sender Policy Framework) record can be used to authorize a domain or IP from which mail is sending and it is a type of DNS TXT record.

If you have your own. and SPF record then there is a chance of the mail getting rejected by the recipient’s server.

Having a valid SPF record will improve the authenticity and deliverability of your emails.

  • Check if the recipient server has the correct MX record

If the recipient’s server MX record is not valid it will not allow sending the mail from your server to that recipient.

If you are still struggling with this SMTP issue, you need to find the exact cause of the issue and find a permanent solution for it also. Our technical support team with having good knowledge in many kinds of mail server-related issues is available here to assist you at any time.

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