Emails from one sender not reaching me

[KevinPSC]

I receive regular emails form one important sender, and received a couple over the weekend.  Suddenly they are not reaching me but I know from another source that at least 3 emails have been issued in the last 48 hours.  There is nothing in spam. Is there are way of whitelisting this sender?

[KevinPSC]

Thanks again for your help.  Much appreciated.🙂 

[Gondola]

For that domain there's just one sending IP address. That IP address is on a spam blacklist albeit for an agency that doesn't have a strong reputation itself but nevertheless it's listed which means the agency is suggesting that spam has been detected. It's therefore possible that the TalkTalk Mail servers are deferring mail for scanning as a precaution. Deferring means delayed delivery.

What can then happen is the TalkTalk Mail servers bounceback a message to the sending mail service, in this case sendgrid. The bounceback is not a rejection of the mail but just an alert for a temporary delayed delivery.

Nevertheless that can have the effect that the Sendgrid mail servers will add the email address to a suppression list and that will stop the sending of further mail. ie. Sendgrid are dealing with the bounceback as a permanent failure to deliver not the reality of a temporary delayed delivery.

If the mail delivery has stopped altogether, not just delayed, then either TalkTalk are blocking the IP address because suspicious content has been detected or other users have marked the mail as spam. OR sendgrid have got your email address on their suppression list.

You could contact the originator and ask if their email admins could check that your email address is not on the sendgrid suppression list.

[KevinPSC]

Hi, thanks for the reply.  The domain appears to be @sendgrid.charterhouse.org.uk

[Gondola]

TalkTalk doesn't offer whitelisting as that's a potential open door for spammers. Especially so if you're asking to whitelist a shared mail sending service.

What's the email domain that you're not currently seeing?

Select one of the mail messages that did get through. Select View source to view the raw email header. What's the email domain contained within chevron brackets for the line that starts Return-Path:

Return-Path is normally at or near the top of the email header.  Knowing that email domain I can check some details for you.