PEAR mail for SMTP authenticate using 3rd party smtp server

Hi

I am trying to set up PEAR mail using a 3rd party smtp service.

I have set up a newsletter mailing list which works using PEAR mail (unauthenticated).
I have gone through the process of finding out the PEAR path on the server and setting up the open_dirbase server settings.

Using unathenticated I use mail.domainname.co.uk on port 25 as the smtp server and email send fine

However I need to use a 3rd party authentication service for the mailing list to avoid hosting/sever overload issues etc

I have found a company authsmtp.com which offers the service. They effectively give me the username/password for email accounts that I allocated on their system as being valid.

The smtp server needs to change from mail.domainname to mail.authsmtp.com and they recommend port 2525

However the PEAR mail path will be on my server, so I need to maintain the pear path.
But if the smtp server changes how does the WA UEmail recognise the domain path to find the pear mail.php file.

I think I will need to use the wizard to create the base WA files and then manually edit them to apply the 3rd party configuration.

Can you please advise, as I currently can't get it to work when using authenticated

Thanks
Nathan