topic Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message in Email

Webmail sending gets a "SMTP Error (535): Authentication failed" message

MoonMan — Wed, 30 Sep 2026 14:23:07 GMT

This is the latest Greenby hiccup to hit me.

I'm using a web browser to access one of my mailboxes. I log in and can read my inbox just fine.

When I try to send an email - it fails with this message.

How can my authentication fail when I've logged into a greenby server and it's doing the sending?

I'm a <mailbox>@<username>.plus.com user who migrated months ago and this hiccup is recent.

Thanks

Sorry if this has already been covered - what threads I could find didn't quite fit my issue.

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

PhilipHeyes — Wed, 30 Sep 2026 14:34:11 GMT

If you reset the password on the problem email a/c does the SMTP Error clear ?

The password can be reset from in the Greenby Portal or in the Greenby webmail.

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

MoonMan — Wed, 30 Sep 2026 14:47:45 GMT

Nope.
Reset in the Greenby portal. Logged into webmail. Can read inbox but sending still fails.
Thanks

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

PhilipHeyes — Wed, 30 Sep 2026 15:11:07 GMT

In the Greenby portal raise a Support Ticket.

Start with REF < email address >

Detail the problem, include the error message.

Specify that you have reset the password via the portal and the problem persists.

Ask for an agent to investigate the problem.

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

Townman — Wed, 30 Sep 2026 17:04:48 GMT

@MoonMan

Which WEBMAIL service? PN's (in PN purple) or Greenby's (Round Cube native colours)?

These services are not the same, PN's use relay.plus.net whilst Greenby's use their naked SMTP servers.

Plusnet's relay.plus.net service was reconfigured last night. That could be just coincidence or it could be directly relevant.

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

PhilipHeyes — Wed, 30 Sep 2026 17:44:04 GMT

Links are :

https://webmail.greenby.com/

vs

https://webmail.plus.net/ ( as migrated customer, I can now not longer send via this route )

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

Townman — Wed, 30 Sep 2026 17:56:24 GMT

@PhilipHeyes wrote:

https://webmail.plus.net/ ( as migrated customer, I can now not longer send via this route )

Hi Phil,

Odd, I can - I double checked things before posting above. What do you encounter?

Is the webmail identity expressly referenced in the Greenby portal?

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

PhilipHeyes — Wed, 30 Sep 2026 18:37:30 GMT

@Townman

Previous must have been a glitch.

I re-tested just now again using the Plusnet webmail the send to my BT Internet a/c and it worked perfectly.

The out bound server was ashbel.gateway.enmail.co i.e send via the Greenby service.

Re: Webmail sending gets a "SMTP Error (535): Authentication failed" message

MoonMan — Fri, 02 Oct 2026 22:08:01 GMT

@PhilipHeyes

@Townman

Thanks for your suggestions. The problem is now understood and sorted-ish!

My web browser had saved the login Username in the old PlusNet format of <username>+<mailboxname>.
I've changed this to the mailboxes E-mail address - <mailboxname>@<username>.plus.com.

Other issues I also had with webmail were:-

the server based 'Contacts' had vanished from all my mailboxes.
the mailbox Identities had changed to a weird format.
the Inbox could be read just fine but again the displayed mailbox name was the weird one.

I'd raised a ticket with Greenby about the missing Contacts and the solution was to alter the login username, which fixed everything.

I was using https://webmail.greenby.com/ by the way.

What confused me was that with the 'wrong' username, I could still access my Inbox but other features failed.
Thunderbird and the Gmail mobile app both still work using the old PlusNet format username, sending to relay.plus.net.

I need to get the 'newer' configs for TB etc. before Greenby make any more tweaks. That's my next job.

Thanks again.