Oooh, I can unfotunately add my own here.
HP printers!
Went to change the SMTP gateway.. Changed it, tested settings, received test email, emailed colleague to advise resolved and closed case.
He responded with the same error message. I was very confused.. Went back to the backend web portal and found the setting I'd changed was reverted back.
So this time, I went through carefully seeing what I'd missed and you see I did not factor in HP's appalling illogical software design!
So you go into SMTP settings. Change the config, test it etc..
And then click finish:
And receive a lovely "This operation was completed successfully" which one would assume means setting has been changed and you're good to go!
NO! it changes it but doesn't save it.
If you simply close the webpage, it'll default back to whatever you had previous.
I found out the hard way, you also need to click a second "Apply" in the main page!
To which you also get the exact same ""This operation was completed successfully"!
HP = Finding new ways to screw over their consumers since forever.