Great blogger gear! When a comment is made, the page refreshes with multiple lines of errors as below for several lines - 123 to 126:
"SMTP Error: Could not connect to SMTP host.
Warning: Cannot modify header information - headers already sent by (output started at /home/infocent/public_html/journal/zp-core/zp-extensions/PHPMailer/class.phpmailer.php:586) in /home/infocent/public_html/journal/index.php on line 123"

When the page is refreshed again, the errors disappear, the comment appears but an error appears in the new comment box.
I do receive an email with the comment though.

Update to problem - I uninstalled PHPMailer and it all works fine??? I assume I don't need it for comments? Is there another use for it that won't conflict with comments?

Zenphoto has two possible mail handlers depending on your needs. There is a simple sentMail implementation and a more involved SMTP, etc. handler. What you use, if any, depends on your server configuration.

If you have no mail handler then Zenphoto cannot send any mails at all. Comment notifications are just one such.

Ok I'm confused. I've uninstalled PHPMailer and the comments work and get mailed to me.
However, even before I uninstalled it, I couldn't get a contact form put in but I assume that's a parameter within the theme I'm using?

There are two mail plugins, the phpmailer and zenphoto_sendmail. The first is more complex and lets you mail via a mail provider while the 2nd just uses the php internal mail functionality if configured on your server. You cannot enable both at the time.

The contact_form is a plugin. The official themes have a special theme page that independently needs to be enabled via the theme options. However you can add the contact_form on other pages naturally.

Thanks. I'll play with it. I'm using Effervesence but haven't been able to work out how to place the cmd in wherever?

What didn't you work out exactly? The theme has built in support for the contact form.

Hmmm. I ticked the contact form plug in, set the paramaters under its options - and assumed it would be placed on the front page somewhere? Or do I have to put code in somewhere?

If you are using a official theme you will get a link somewhere to the contact page if you enable the theme's option for that.

If not you have to add the function where you wish it to appear. Generally plugin don't add themselves to any theme unless it has support. Zenphoto themes give you complete freedom of layout so there are not fixed places where plugins always add (this is actually note above the plugins tabs as well).