topic Re: k9 mail certificate error - sending to relay.plus.net in Email

k9 mail certificate error - sending to relay.plus.net

geoffers — Fri, 15 Aug 2025 12:37:40 GMT

Hi - I have been using K9 email client on phone/tablet for yonks with zero problems, but sending from K9 now gets certificate error (CertPathValidatorException - trust anchor for certification path not found) so don't know if this is something changed in K9, or something has changed at relay.plus.net

There are no problems sending to relay.plus.net using Outlook on the PC

The K9 settings which have worked OK until today have StartTLS; port 587; Normal Password; Username; Password and Client certificate = None (no other options provided)

If I go through the config settings in K9 it now gives this message

Any ideas...?

Re: k9 mail certificate error - sending to relay.plus.net

jab1 — Fri, 15 Aug 2025 12:56:09 GMT

@geoffers Which phones tablets - make a model? Sounds like a known issue.

Re: k9 mail certificate error - sending to relay.plus.net

Dan_the_Van — Fri, 15 Aug 2025 13:02:27 GMT

@jab1

can you confirm if you can see the image please? A thanks will be enough

Re: k9 mail certificate error - sending to relay.plus.net

jab1 — Fri, 15 Aug 2025 13:08:14 GMT

@Dan_the_Van I can now, but couldn't when I posted my initial reply.

Re: k9 mail certificate error - sending to relay.plus.net

Townman — Fri, 15 Aug 2025 13:21:48 GMT

@jab1 wrote:

@geoffers Which phones tablets - make a model? Sounds like a known issue.

John,

Sounds similar to the known issue, but is not the same as the known issue.

The known issue relates to INBOUND sever certificates and the failure of some device vendors to supply CURRENT G5 root certificates to their users.

This issue relates to OUTBOUND server certificates which look as though they were installed today ... and DO NOT use the G5 certificates...

PS C:\Users\kevin> curl.exe -w '%{certs}' smtps://relay.plus.net 214-This is smtp ESMTP service help 214-To contact postmaster send email to postmaster@plus.com. 214-For local information send email to Postmaster at your site. 214 end of HELP info Subject:1.3.6.1.4.1.311.60.2.1.3=GB, 2.5.4.15=Private Organization, serialNumber=03279013, C=GB, L=Sheffield, O=Plusnet plc, CN=relay.plus.net Issuer:C=US, O=DigiCert Inc, CN=GeoTrust EV RSA CA G2 Version:2 Serial Number:06:ad:2c:f1:7b:de:0a:7e:2f:8c:b8:09:4a:b9:01:81: Signature Algorithm:sha256WithRSAEncryption Start Date:2025-08-15 00:00:00 GMT Expire Date:2026-08-14 23:59:59 GMT

We have flagged the issue to the business.

Re: k9 mail certificate error - sending to relay.plus.net

jab1 — Fri, 15 Aug 2025 13:25:51 GMT

Cheers, @Townman . You can tell I'm a little out of touch.😀

Re: k9 mail certificate error - sending to relay.plus.net

geoffers — Fri, 15 Aug 2025 13:30:59 GMT

@jab1 - Thanks: Phone is OnePlus9 running android 14
Tablet is Lenovo P11 Pro running android 11

Re: k9 mail certificate error - sending to relay.plus.net

Townman — Fri, 15 Aug 2025 13:35:52 GMT

@jab1

Nah John,

It is not a matter of being 'out of touch' but discerning detail. There are so many bullets in the air, that there is a danger of seeing them as all being the same. INBOUND has been around all week; this OUTBOUND issue is new, though why is not clear.

We have this escalated.

Re: k9 mail certificate error - sending to relay.plus.net

geoffers — Fri, 15 Aug 2025 13:39:47 GMT

@Townman and @jab1 - don't know if this helps, but I just pulled out an old Motog5 phone which is sending emails OK from k9 - however in this phone's SMTP setting it had Security=None whereas the OnePlus & Lenovo settings has Security=StartTLS

Re: k9 mail certificate error - sending to relay.plus.net

Townman — Fri, 15 Aug 2025 13:41:59 GMT

@geoffers

That does not in the sense you indented help: The issue is connected to the encryption security certificate. If you use the SMTP server without encryption, you will not encounter the issue with the certificate.

Re: k9 mail certificate error - sending to relay.plus.net

jab1 — Fri, 15 Aug 2025 13:42:44 GMT

@geoffers More @Townman 's field of expertise than mine, so I'll keep quiet 😁. The issue has been noted, though.

Re: k9 mail certificate error - sending to relay.plus.net

Townman — Fri, 15 Aug 2025 15:01:37 GMT

@geoffers

Can you please give it another go - the certificates have been updated.

Re: k9 mail certificate error - sending to relay.plus.net

geoffers — Fri, 15 Aug 2025 15:03:39 GMT

Brilliant - looks like that fixed it, thanks 😎

Re: k9 mail certificate error - sending to relay.plus.net

Anonymous — Fri, 15 Aug 2025 22:11:50 GMT

indented

Help

(Has anyone seen my coat?)