Unable to send emails over mobile wifi hotspot

[#1]

Hello,
I have a frustrating problem in that I often need to use my mobile to create a wifi hotspot for accessing the internet using my laptop when I am in remote locations. In the part this works well and I can receive emails with no problem but sending via thunderbird just won't work. I get a repeated Login failed message despite entering the correct password.
No problem at all when I am connected directly to any other ISP and router. I've tried using the same settings as my mobile for via smtp.plus.net and also the settings I normally use via relay.plus.net but neither will send mails.
This seems to be a problem with Plusnet? How can I resolve it and send emails? Using webmail.plus.net isn't an option so please don't suggest this.
Thanks

[#2]

which mobile network are you connected to

[#3]

Hi, and welcome to the PN forum.
Sending email via relay.plus.net requires SMTP authentication if you're not using the Plusnet network.  For some reason, the published setup guide turns off authentication in section 8
http://www.plus.net/support/email/setup/thunderbird-setup.shtml
Set it back to Password, Sent Insecurely and try again.
HTH

[#4]

Hi,
I have SMTP authentication enabled, hence the reason I can connect OK via any ISP/Router.
My network is orange. I've read that this could be the problem.
If this is the problem what I don't understand is how I can send/receive email ok via plusnet directly from the mobile over 4G using the imap and smtp.plus.net services..
Thanks

[#5]

What do you have the SMTP port set as?

[#6]

I have tried 25 and 587 which appear to be defaults?

[#7]

I'd use 25 with relay.plus.net.
For testing purposes, are you using your mailbox (username+mailbox) or just the main account (username) for sending mail?

[#8]

I've tried both, neither work, both result in the same error.

[#9]

some providers block port 25

Quote from: Oldjim

which mobile network are you connected to

is a relevant question..

[#10]

I already put which mobile network I'm using.

Quote

My network is orange. I've read that this could be the problem. If this is the problem what I don't understand is how I can send/receive email ok via plusnet directly from the mobile over 4G using the imap and smtp.plus.net services..

[#11]

Do they have any particular restrictions on what you can do while your using your phone as a mobile hotspot?

[#12]

Can you try manually accessing the PN server to see if it is blocked?
The response to 'telnet relay.plus.net 25' and/or 'telnet relay.plus.net 587' will show if it is a fundamental access issue...

[#13]

I tried and it connected, this was the response from relay.plus.net

Connected to relay.plus.net.
Escape character is '^]'.
220 avasout02 smtp relay.plus.net

The other port also works..
I think it is related to authentication. But I don't understand why?

[#14]

That certainly confirms that the ports aren't blocked. 
I haven't tried it, but there's some instructions here on testing SMTP authentication manually here:
https://www.ndchost.com/wiki/mail/test-smtp-auth-telnet
and a tool to encode your username and password here:
https://www.base64encode.org/
I think you'll need to start ploughing through Thunderbird logs...

[#15]

The Community Support Library article Testing SMTP Authentication gives instructions for checking authentication on relay.plus.net.