One of the many reasons you should always Use strict and warnings. Look closely at the variables in your loop:

foreach $file (@TIFFfolder_list){
my $file = basename (@TIFFfolder_list, ".psd");
print "$file\n";
}
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You've got two $file variables there: the package variable you're using as the loop variable, and the new lexical one you're declaring with my. But you're not passing either of those to the basename function...

BTW, the File::Basename doc says that fileparse is a bit safer - and where are you loading that module in the first place?

You're printing the filenames to standard output, but then you're using -body=>"$file", but the variable should be empty at that point. Perhaps you want to set up a new variable into which you concatenate your output via .= instead (or use the map/join solutions others have alluded to).

Also, note that the Mail::Sender docs say the module is deprecated, use Email::Sender instead.