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Our Customer Emails Are Getting Bounce Back

First Timer
Message 3 of 3

We're Web Hosting Company based in UK. Few of our customers who are using TalkTalk email aren't able to receive emails regarding their services. Please check SMTP logs below:


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: host [] SMTP error from remote mail server after initial connection: 554 cm10nec oaHFmExEzDrDP IP Blacklisted (TT104) Attachment blocked - file type not allowed.

Our Mail server IP address:

Please unblock our IP address.


Support Team
Message 1 of 3

Hi wehosttech, Gondola's advice is always spot on.  You'll need to improve your server sending reputation.



Please log in to My Account if you need to view or pay your bill, manage boosts and track your usage. From My Account you can also check your connection and test your line for any issues in the Service Centre.


Community Star
Message 2 of 3

Hi wehosttech 


The mail server IP address is currently on the UCEPROTECTL3 spam blacklist. This blacklist is normally associated with mail services gaining a low reputation due to hosting spammers. When your servers cease to send 'spam' the blacklisting does automatically expire.


What actions have you taken to improve the server reputation? Have you scanned the outgoing mail and checked the attachment? Might the attachment be an exe file? Whatever it is, the attachment is not acceptable to the talktalk mail servers and continuing to host this mail would not, in my view, help to improve your server reputation.


You originally posted an active talktalk email address as the recipient rejecting the mail. The TT104 error is a bounceback advising that your sending IP address is blacklisted. The reason given for the rejection of the mail is because the attachment is not acceptable. The bounceback also gives a Cloudmark reputation remediation request.  TalkTalk use Cloudmark to assess the incoming mail for potential threats. You could request Cloudmark to unblock your mail servers but if the unacceptable attachments continue to be received these will be trapped by Cloudmark and the blocking will continue.


The actions to take are, I think, in your hands and dealing with the source of the issue as the way to improve your server reputation.


NB this is not a TalkTalk opinion as I'm just a volunteer to the TalkTalk community. You'll likely get a TalkTalk Support response from Monday onwards.

GondolaVolunteer 2017-2022

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