Cannot send emails when connected via a 3MiFi unit

[#1]

I've been having line speed problems with my fixed phone-line (long line app. 6.6km from BT exchange ) so I'm currently evaluating a 3mifi unit.
The speed improvement is amazing but when I try to use my  Plus net email account (using Firefox) when connected via the 3mifi unit I can receive messages OK but I can't appear to send any messages. I have tried changing the port number for the O/G SMTP server using 465, 485 or 587 but none of these work.
Any ideas or suggestions?

[#2]

Oops sorry I started another thread on this topic - should have searched threads first.
But just to add to the (original thread) the 3 support page for email problems suggests changing FROM port 25 to either 465, 485 or 587.
Also I have just set up a Gmail account and that works fine ie. send and rxd work perfectly OK.

[#3]

Plusnet only support sending via port 25 at present and 3 block port 25, so you have to send using their servers.

[#4]

Quote from: dvvrue95

suggests changing FROM port 25 to either 465, 485 or 587.

In general, that would be good advice, but it doesn't work with relay.plus.net because Plusnet only accept connections over port 25. As you no doubt saw in the other threads on the subject, you have to send via 3's own server if you want to send from your existing email addresses, rather than from a Gmail account.
In case you need it, the smtp server to use is smtp-mbb.three.co.uk, port 25, no authentication. Then you should be able to send from any email address you like.
Ah - see jelv has beaten me to it!

[#5]

Hi
@ jelv and Simon M
If I have read your post correctly they seem to contradict each other on the use of port 25. I have posted a reply in the thread below.
I will end this thread now since it is duplicating some of the comments in the thread "Unable to send email using Three MiFi dongle".

[#6]

No, we're both saying the same thing, just slightly differently.
You can't use the Plusnet server at relay.plus.net, because it only works with port 25 & three won't let you sent port 25 to anywhere other than their own servers. So you have to use smtp-mbb.three.co.uk, port 25, no authentication as your outgoing server.
That is quite separate from the mailbox account settings, which means that you can send *from* your Plusnet email address, but *via* the three smtp server.
If you have a choice, this type of setup is much more instinctive to set up in Thunderbird than it is in Outlook (or it is to me, anyway).
I can't offer any help on the error message you are getting - it says it's temporary, but I can't see if I get the same message because I'm out of credit. I'm on a PAYG deal & I only load it up if I'm travelling, which I won't be for a couple of weeks yet.