all mails to @talktalk.net addresses rejected with "Content deferred (TT991)"

[herves]

Hello,

I am part of the tech team at Ember buses (www.ember.to). We use email to send out bus tickets to our passengers. For the past 48h or so we've been unable to send messages to any @talktalk.net address. The email server at mx.talktalk.net responds with "Content deferred (TT991)".

Nothing has changed recently at our end, we've been sending these emails to talktalk.net addresses for years without issues. The emails come from ride[at]ember.to and don't have attachments. We never send unsollicited emails -- all messages are triggered by our users e.g. when they purchase a ticket.

This seems similar to the issue described at https://community.talktalk.co.uk/t5/Email/Unable-to-send-to-talktalk-net-and-tiscali-co-uk-Content/m... The comments there suggest it might be due to the CloudMark software that TalkTalk uses, could that be where the problem is?

Any help would be greatly appreciated.

Many thanks

Hervé

[herves]

Hi Ady,

Thanks a lot for the reply and for looking into this. 

Just to clarify, the emails are not technically blocked, they're just deferred for so long that the sending server eventually gives up (after e.g. over 48 hours of receiving "Content deferred (TT991)" on every attempt).

That being said, things seem to be improving in the last 24 hours. Most of our messages are now eventually reaching their recipient's inbox. Many emails still get deferred several times, but do get through on the 5th or 10th attempt. So consider this resolved.

Thanks!

[Ady-TalkTalk]

Hi herves,  I've run the 7 day scan and it shows no mail blocked from the specified email address. 

Ady

[Gondola]

TT991 Content deferred means that mail is not blocked but just delayed for scanning.

A bounceback error message of code TT992, on the other hand, means that mail has been rejected.

I can see that Google mail servers are in use for your mail messages and that there is a valid SPF file in place to authenticate the sender. There would normally be no reason to block such emails unless multiple TalkTalk customers have marked the emails as unwanted spam instead of unsubscribing. It may also be the case that although Google have many mail senders available they just happen to be using one that's been blacklisted and that's being used currently for your mail messages. Your email address is not on any of the usual agency blacklists.

I'll alert TalkTalk Support to check the network filtering for reports of blocking over the last 7 days.