Outgoing SMTP from Android tablet

[#1]

Hi All,
I'm trying to get outgoing SMTP to work from an android tablet (Samsung galaxy tab 3). It is a wifi-only tablet so it is definitely connecting to the internet via my PlusNet Router and not via any 3G connection. I have tried three sets of settings:
Settings 1a:
Server: relay.free-online.net
security type: none
Port 587
Require sign-in (tick)
user name: username+mailboxname
Password: mailbox password
Settings 1b: as above but
user name: username
Password: main account password
Settings 2:
Server: relay.free-online.net
security type: none
Port 25
require sign-in (untick)
Settings 1 and 2 are demonstrated to work from Windows and Linux boxes connected to the same network. But they won't work from the Samsung device. I am using the default email client that was supplied with the device: I have not experimented with extra email clients.
Any suggestions welcome!
Hugh

[#2]

I should add that if I set up settings 1a or 1b with the wrong password then the tablet checks the password and says that it is wrong. If I use the correct password it accepts it. So it is contacting the SMTP server when I set it up and ensuring that the password is OK. But it still won't send an email: they all end up in the outbox with messages to the effect that sending of the email failed.
Hugh

[#3]

I got this to work in the end by removing the account details from the tablet and entering all the details from scratch, and all in one go, without making any mistakes with the password.