H wanted a new mailing list, for which he supplied email addresses in an excel sheet. The easiest way to import these into phplist, since he did not want any customization, was as a simple list of emails, one per line - phplist can import such a list with minimum of fuss. Unfortunately, even that took a while - the list had many typos, so phplist was barfing it up. After H did cleanup using some tool, tried the 18,000 email list at once, phplist did not respond. Then cut it up into smaller pieces - upto 6000 emails per file was imported without any problem.