It seems a little strange to my eyes but Evolution cannot import Outlook PST files. On one level, I see a certain amount of sense: after all, Outlook is a Windows application and Evolution remains resolutely on the Linux side of the divide. Nevertheless, it is still a pesky nuisance. The cure is, very oddly, to import data from Outlook into Mozilla Thunderbird and pop the Thunderbird files into the Evolution mail folder. Both Evolution and Thunderbird share the same file formats so all is hunky dory since Evolution should just realise that they are there and bring them in. That’s what happened for me and I have now migrated all of my old emails. Evolution’s single file import wizard is there for those times when a spot of extra persuasion is needed; the data files are those without the file extensions. As it happened, I didn’t need it.