It turns out they are using gmail to access emails on this account, so presumably I should be able to use the gmail settings.
I tried the following:
Email object: Mail
SMTP server: smtp.gmail.com
That didn't break anything, in that a test to my email address worked, and I received the UE generated email correctly.
But it doesn't seem to have been delivered to an email address we knew we were having problems with.
Email object: PEAR Email using SMTP
Username: The email address
Password: The email address password
SMTP server: ssl://smtp.gmail.com
Using those settings, it gets as far as reloading the page that has the form that triggers the email, but it gets stuck with just a white page, so assume its failing at some of the UE code above the header.
Path to PEAR was blank - does anything need to go in there?