Email send fails / SMTP Certificate

[#1]

@PhilipHeyes 

I am not convinced that security certificates are issued by Plusnet - I think they come from elsewhere in the BT hierarchy.

@plusnettony 

Is an update available yet please?

[#2]

@Townman 

Plusnet is named in both the G2 & G5 Certificates.

BT's email server mail.btinternet.com has DigiCert Inc, GeoTrust TLS RSA CA G1 for IMAP/POP3/SMTP

[#3]

@PhilipHeyes 

Indeed they are the internal certificate names, but I am aware that a deal of network stuff is handled at BT Consumer Division level.  I firmly believe that if this issue was solely in the gift of Plusnet technical services, it would have been fixed two weeks ago.  This is not that difficult - ask the supplier to reissue G2 root certificates OR declare that G5 is the standard by policy ... and apply it consistently.  It is an exact replica of the 2025 failures ... which took orthogonal escalation to resolve.

I suspect that some IT Security 'guru' thinks this is a beneficial policy, whilst leaving inbound on G2 is acceptable ... as is having unauthenticated SMTP server access.  Certificate suppliers supply what is asked for - in this case G2 on inbound and G5 on outbound.  Suggesting that the certificate issuer is "doing their own thing" was the early line in 2025.  For me the statement holds no credibility; if it were true, they why would the inbound certificates not be G5 also?

[#4]

We've identified a potential solution for the email connectivity issues affecting some customers using older devices and email applications.

A change has been scheduled for 2pm tomorrow, subject to final approval, to deploy an alternative SSL certificate that is expected to improve compatibility.

Once the change has been completed and verified, we'll provide a further update to confirm the outcome.

[#5]

New certificate appears to be in place...

Subject:C=GB, L=Sheffield, O=Plusnet plc, CN=relay.plus.net
Issuer:C=US, O=DigiCert Inc, OU=www.digicert.com, CN=GeoTrust TLS RSA CA G1
Version:2
Serial Number:02:41:89:41:c5:4d:1e:c5:4a:67:3b:88:c1:1a:01:07:
Signature Algorithm:sha256WithRSAEncryption
Start Date:2026-08-28 00:00:00 GMT
Expire Date:2027-03-14 23:59:59 GMT
Public Key Algorithm:rsaEncryption
RSA Public Key:2048

[#6]

Slight apologies, this mornings message was from yesterday, so the 2pm actually referred to today.

As @Townman states, it's in place.

[#7]

Certificate check passed for SMTPS (465) via relay.plus.net with the GeoTrust TLS RSA CA G1 certificate
when using Gmail & Blue Mail on Android 13. 

So migrated customers can send via the Greenby enmail.co platform and keep email admin to the www,greenby.com portal,
can the same Certificate be deployed to relay.force9.net and to relay.free-online.net ? 

[#8]

Thanks to whoever and however this has been fixed.

I don't pretend to understand it fully - it seemed earlier to be a problem with phones being out of manufacturers' support, but I guess that wasn't the cause. Or maybe it was.

I can confirm that Outlook (Android) is now able to send as well as receive email without my having to make any changes to settings. I held off fiddling with settings as, with Outlook, you can't edit account settings once they've been set. You would have to delete your account and start again.

In any case, it's working again. For now.