# README
go-imap-backup
Backup, restore and delete old messages from an IMAP server.
Usage
go build, then go-imap-backup [-flags] command, where command is one of:
queryfetch folder and message overview from IMAP serverlqueryfetch folder and message metadata from local storagebackupsave new messages on IMAP server to local storagerestorerestore messages from local storage to IMAP serverdeletedelete older messages from IMAP server
Flags must be given before the command. The available flags are:
| Flag | Description | Default |
|---|---|---|
| -s | IMAP server name | (read from console) |
| -p | IMAP port number | 993 |
| -u | IMAP user name | (read from console) |
| -P | IMAP password | (read from console) |
| -l | Local storage path | (server)/(user) |
| -m | Age limit for deletion in months, must be positive | 24 |
| -f | Force deletion of older messages without confirmation prompt | false |
| -r | Restrict command to a comma-separated list of folders | (blank) |
| -R | Number of retries for failed operations | 3 |
| -d | Delay in seconds between retries | 10 |
Local storage
Backups are stored locally in a directory tree server/user/, which is created by the backup command if necessary. For each folder on the IMAP server, the local directory contains both a mailbox file named folder.mbox, and an index of the messages therein called folder.idx.
The .mbox files follow mboxo format as defined here. That is, they do not quote lines starting with From . This preserves message sizes, checksums and signature validities. The backup tool avoids ambiguities arising from this by always addressing the .mbox file according to the indices and offsets in the corresponding .idx file.
The .idx file is a text file with one newline-separated line per message. Each line consists of the following tab-separated columns:
| Column | Description |
|---|---|
| UidValidity | A unique 32-bit integer identifier for an Imap folder |
| Uid | A unique 32-bit integer identifier for a message inside an Imap folder |
| Size | The size of the email message in bytes |
| Offset | The starting offset of the email message in the .mbox file |
Note that the offset points directly at the start of the message itself, not at the separator line From [email protected] timestamp preceding it in the .mbox file. The size is the exact size of the message as well, excluding the blank separator line following the message in the .mbox file.
License
Libraries used
This project uses a number of open source libraries. Please refer to their respective repositories for licensing terms.