By default nothing is stored: a message arrives, it is forwarded, no copy is kept.

The mailbox changes that on purpose. With it enabled, mail can be delivered into a mailbox here and read with any IMAP client, without a second provider in the picture.

When it is the right choice

• You want an address that does not depend on a mail provider you would rather not have.
• You want replies from an alias without the forwarding round trip.
• You are moving away from a provider and need somewhere for mail to land in the meantime.

What it needs: a key

Nothing is written to our disk in readable form, so a message is stored only in one of two cases:

• It can be encrypted to your OpenPGP key, which means a key on your default recipient.
• It arrived already encrypted end to end, in which case it is stored exactly as it came, byte for byte, so a client that does its own encryption finds the message as the sender wrote it.

Without a key, mail that is not already encrypted is not stored at all. That is a deliberate stop rather than a silent fallback to plain text: the whole reason to keep mail here instead of forwarding it disappears the moment it sits readable on somebody else's disk.

What it costs

Storage here. A gigabyte per account, which is a lot of text mail and not much of anything else.

And a different privacy position, stated plainly: forwarded mail passes through and is gone, mailbox mail sits on a disk we run, encrypted, until you delete it. What Skudo stores about you is specific about the difference.

Turning it on

Under Mail provider. Turning it off later stops delivery into the mailbox and leaves forwarding as it was.

Connecting a client

See Connecting a mail app.