I've no experience of mail servers, but I get the impression that Postfix is quite popular. It's described as being very similar to Sendmail, but simpler internally and easier to set up.
Thanks Eric,
It's not a mail server I want, it's simply a retriever. For sending mail from within scripts I find the basic 'mail' command does what I need.
I want to retreive mail from the remote server (gmail in this case) packaged up into files that can be read by other mail clients, it's just a back up to cover the unlikely scenario where google might let me down by losing all my mail. It also came in useful on one occasion when I managed to accidentally delete a mail item that I regretted; it was long gone on the server by the time I reallised, but I was able to retrieve it by digging out the corresponding backup.
getmail works a treat one you get it going, it's been running well for a year or so. But an IMAP retrieval has the potential to do massive damage if it were buggy by deleting stuff on the server, so you need to have something you can trust.
edit, PS: To clarify, Burakkucat has pointed out that I might have a lot more trust if I used a distribution other than Fedora. That has been noted I'm already convinced he is right. But come the day I build a new (not Fedora) server, I shall still face the dillema of whether to continue with getmail, or something else...