Hello all, i am not sure if plain webmail is the right category for what i’m looking for.

I already have a mail server running in a hosting VPS that has been running for years and handles sending and receiving emails without issues or being flagged as spam, what I’m trying to accomplish is:

• Handling the storage of very old and large mailboxes (imap 20gb+) to my local server since my VPS is runing out of space.
• Continue using the VPS email server to receive/send emails. Since i’m not at all interested in selfhosting the email server and dealing with all those issues.
• Multiuser since several family members have the same issue.
• Selfhosted so we can check/send email from any device/mobile.

Something that works similar (but obviously not selfhosted) is adding a POP3 account to Gmail/Outlook/etc and then adding the “send mail as” SMTP credentials of the server. I would like to replicate the same but selfhosted if possible.

Is there anything that works like this?