Auto-Reply¶

Set up automatic out-of-office replies for a mailbox. When enabled, the server sends a reply to the first sender of each incoming message using the contents of a .auto-reply file.

Enable in Config¶

Add an [auto_reply] section to your server TOML config:

[auto_reply]
enable = true
interval = 86400

Parameters¶

Parameter	Type	Default	Description
`enable`	bool	`false`	Enable server-side auto-reply
`interval`	int	`86400`	Minimum seconds between auto-replies to the same sender

Set Up a Mailbox Auto-Reply¶

Create a .auto-reply file in the mailbox directory with the reply body:

echo "I'm currently away and will reply when I return." > mailboxes/alice/.auto-reply

The file contents become the full reply body. To disable auto-reply for a mailbox, delete the file:

rm mailboxes/alice/.auto-reply

No server restart is needed — the server checks for the file on each incoming message.

How It Works¶

When a message is successfully delivered to a mailbox:

The server checks if [auto_reply] is enabled in the config
It looks for a .auto-reply file in the recipient's mailbox directory
If the file exists and the message passes safety checks, a reply is sent to the first sender
The reply uses the server's identity certificate and private key (identity_certfile/identity_keyfile)
The reply subject is set to [Auto-Reply]

Auto-replies are fire-and-forget — they never affect message delivery. If the reply fails (network error, timeout, rejected), the original message is still stored normally.

Loop Prevention¶

The server prevents auto-reply loops:

Messages with [Auto-Reply] in the subject are never auto-replied to
This means two servers with auto-reply enabled will not create an infinite reply loop

Rate Limiting¶

To avoid flooding a sender who sends multiple messages, the server rate-limits auto-replies per sender address:

The interval setting controls the minimum time between replies to the same sender (default: 86400 seconds = 24 hours)
The timestamp is recorded eagerly before sending, so concurrent messages from the same sender won't trigger duplicate replies

[auto_reply]
enable = true
interval = 3600   # reply at most once per hour per sender

Tip

Set a shorter interval (e.g., 3600) during active away periods when senders may write multiple times. Use the default 86400 for standard out-of-office notices.

Requirements¶

Auto-reply requires the server to have identity credentials configured, since it sends messages as the server identity:

[server]
hostname = "mail.example.com"
identity_certfile = "identity.pem"
identity_keyfile = "identity.key"

[auto_reply]
enable = true

Warning

If identity_certfile or identity_keyfile are not configured, auto-reply is silently skipped and an auto_reply_no_identity_cert warning is logged.

Full Example¶

[server]
host = "0.0.0.0"
port = 1958
hostname = "mail.example.com"
mailbox_dir = "/var/mail/misfin"
identity_certfile = "identity.pem"
identity_keyfile = "identity.key"

[auto_reply]
enable = true
interval = 86400

Then for each mailbox that should auto-reply:

echo "Thanks for your message! I'm away until March 1st." \
    > /var/mail/misfin/alice/.auto-reply