Can't send emails - getting a mail delivery failed message mentioning HALO issue, but all settings checked & correct.
I'm currently able to receive, but not send emails from an account that was working 2 days ago. I hadn't changed anything, it's just stopped working. Example of return receipt message:
"This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
[address removed for privacy]
host eur.olc.protection.outlook.com [126.96.36.199] SMTP error from remote mail server after HELO 221.28-188.8.131.52.in-addr.arpa.: 501 5.5.4 Invalid domain name [HE1EUR02FT043.eop-EUR02.prod.protection.outlook.com]
Reporting-MTA: dns; server88.web-hosting.com
Action: failed Final-Recipient: rfc822;[address removed for privacy] Status: 5.0.0 Remote-MTA: dns; eur.olc.protection.outlook.com Diagnostic-Code: smtp; 501 5.5.4 Invalid domain name [HE1EUR02FT043.eop-EUR02.prod.protection.outlook.com]"
I've checked the outgoing server settings as per info I've found online, and all seems correct.
Any ideas what might have happened and what I can do to fix it?
Additional System Details
- User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36
This isn't a Thunderbird issue. The problem is on the SMTP server of the recipients email provider. If it worked before this may be temporary issue, so just try again later. Otherwise check with your email provider if they can help. And you may have the recipient also have to check with his/her email provider.