E mail sending issues

[#1]

I have come to a hotel for a week and am using their Internet - but since arriving I'm having problems sending e mail -  I am getting the following message:- Cannot send mail - the username or password for SMTP username+username@relay.plus.net is incorrect (I have not put my real username for security reasons)
Now my username is not incorrect - I think everything else is ok - I rang PLUSNET last night and the guy said there was an issue with SMTP - so is it PLUSNET or is it me??  I'm having the problems on my I pad and my I phone. Service status does not mention an issue with e mails - it is only sending I am having issues with - I just can't reply to any e mails - HELP!!
Many thanks

[#2]

You can use username+mailboxname with the corresponding mailbox password ( just like you use for webmail ) OR username and password , where these are the main account details ( like you use to login to the portal ). Since everything is in clear text using your main account/password is probably not a good idea. You might also try changing the port to 587 in case the hotel network is blocking port 25 ( unlikely! )