If you've been using VM's webmail then the mails are accessed over IMAP, not POP3.
If you set up an IMAP client then nothing will happen to the mails on the server. The client will download a copy of the mails on the server and in the case of sent mails, will upload any to the Sent folder when you connect. All clients will sync using the mail on the server.
The only drawback is that you have to remember that once a mail is deleted on one device - that change will be communicated to the server and then to all other connected IMAP devices.
Any mails that were "deleted" by any POP3 clients, are left on the server, they're simply hidden from all future POP3 transactions. So if you had been using a POP3 client then mail sent after the server changeover in 2015 (IIRC) will still be there, unless you deleted it in webmail.
Tim
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