Xneelo has informed users that it is experiencing a large-scale spam outbreak that is resulting in email being delayed.
Many Xneelo subscribers have been experiencing delays when sending emails to external recipients.
Some users have also received messages that the IP address they are attempting to send the email from is on the Spamhaus blacklist.
“You will receive the following error when attempting to send an email: 550 Spamhaus (-53): retry time not reached for any host,” Xneelo said.
The message below is what many Xneelo subscribers have received since yesterday:
A message that you sent has not yet been delivered to one or more of its recipients after more than 24 hours on the queue on antispam-jnb1.host-h.net.
The message identifier is: XXXX
The subject of the message is: XXXX
The date of the message is: Tue, 25 Aug 2020 09:20:00 +0200
The address to which the message has not yet been delivered is:
host xxxx.mail.protection.outlook.com [xxx.xxx.xxx.xxx]
Delay reason: SMTP error from remote mail server after pipelined sending data block:
xxx.xxx.xxx.xxx Server busy. Please try again later from [xxx.xxx.xxx.xxx]. (Sxxxxx) [xxxx.prod.protection.outlook.com]
No action is required on your part. Delivery attempts will continue for some time, and this warning may be repeated at intervals if the message remains undelivered. Eventually the mail delivery software will give up, and when that happens, the message will be returned to you.
The company said its engineers have rolled out a change that should resolve the error being encountered.