I have just upgraded my iPhone and cascaded my old iPhone to another family member. When setting up the Zen E-Mail POP3 accounts it results in a download of over 1500 old e-mails per device. I understand that the solution is to go into webmail and delete all unwarranted e-mails. My problem is that no matter what I try, I cannot access Zen Webmail. I have tried doing it on various machines with both Safari and Windows10 - the page just hangs.
Interestingly, I have just added the Zen POP3 accounts to an old IPad and I don't get the same massive e-mail download.
Zen Support is, as increasingly the case these days, not available for comment.
POP-3 by design is not supposed to be used as a long term storage solution. It was designed back in the day where your e-mail would be delivered to a POP-3 mailbox, and then collected when you next "dialled in", and downloaded to your computer, then deleted from the server it was on.
Some devices (Apple Devices are one such) set an option by default that does not send the delete command as it gets messages, so messages remain on the POP-3 server. This works until either the number of messages is so big it takes forever to check them, the mailbox becomes full or other events happen to screw up. It is NOT the expected way for it to be used, so if it breaks, it's sort of your own tough luck really.
When people first started getting secondary devices, a common trick (which wasn't flawless) was that the primary device (your PC) was set to delete messages, but the secondary device (the iPad in this case) was not. In a way this sort of made life easier as the PC got everything, and the iPad the stuff you hadn't yet picked up on the PC. Sent Items and folders etc aren't sync'd as that's not a POP-3 thing, and anything you pick up on the PC before receiving on the iPad it never sees. But it was good enough for some.
However, now we have always on, always checking devices and setups using POP-3 in the manner you describe is a poor plan.
You really want to use either IMAP (as flawed as that is, it is at least designed for multi-device access) or something like a Hosted Exchange type setup. I imagine the latter is not offered by Zen with the included-with-broadband e-mail you have, but IMAP might be - I've never checked.
In the same vein, the reason your webmail etc has those issues is because it again is only really designed to be used as a temporary/occasional thing - and if POP-3 was being used as intended, you'd only have a few messages.
Whilst Zen Support are unavailable, I would politely suggest the issue is really the wrong e-mail setup being used for the job in hand.