The blog post "[Email Setup with isync, notmuch, afew, msmtp and Emacs]({{<relref"email-setup-with-isync-notmuch-afew-msmtp-and-emacs">}})" prompted a few questions. The questions were around synchronizing email in general.
I did promise to write up more blog posts to explain the pieces I brushed over quickly for brevity and ease of understanding. Or so I thought !
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## Maildir {#maildir}
Let's talk **Maildir**. [Wikipedia](https://en.wikipedia.org/wiki/Maildir) defines it as the following.
> The Maildir e-mail format is a common way of storing email messages in which each message is stored in a separate file with a unique name, and each mail folder is a file system directory. The local file system handles file locking as messages are added, moved and deleted. A major design goal of Maildir is to eliminate the need for program code to handle file locking and unlocking.
It is basically what I mentioned before. Think of your emails as folders and files. The image will get clearer, so let's dig even deeper.
If you go into a **Maildir** directory, let's say **Inbox** and list all the directories in there, you'll find tree of them.
```bash
$ ls
cur/ new/ tmp/
```
These directories have a purpose.
-`tmp/`: This directory stores all temporary files and files in the process of being delivered.
-`new/`: This directory stores all new files that have not yet been _seen_ by any email client.
-`cur/`: This directory stores all the files that have been previously seen.
This is basically how emails are going to be represented on your disk. You will need to find an _email client_ which can parse these files and work with them.
## IMAP {#imap}
The **Internet Mail Access Protocol**, shortened to **[IMAP](https://en.wikipedia.org/wiki/Internet%5FMessage%5FAccess%5FProtocol)**, is an
> Internet standard protocol used by email clients to retrieve email messages from a mail server over a TCP/IP connection.
In simple terms, it is a way of communication that allows synchronization between a _client_ and an _email server_.
## What can you do with that information ? {#what-can-you-do-with-that-information}
Now, you have all the pieces of the puzzle to figure out how to think about your email on disk and how to synchronize it.
It might be a good idea to dive a little bit into my configuration and why I chose these settings to begin with. Shall we ?
## isync {#isync}
Most _email servers_ nowadays offer you an **IMAP** (**POP3** was another protocol used widely back in the day) endpoint to connect to. You might be using _Outlook_ or _Thunderbird_ or maybe even _Claws-mail_ as an _email client_. They usually show you the emails in a neat **GUI** (Graphical User Interface) with all the _read_ and _unread_ mail and the _folders_. If you've had the chance to configure one of these clients a few years ago, you would've needed to find the **IMAP**_host_ and _port_ of the server. These clients _talk_**IMAP** too.
[isync](https://isync.sourceforge.io/) is an application to synchronize mailboxes. I use it to connect to my _email server_ using **IMAP** and synchronize my emails to my hard drive as a **Maildir**.
### IMAP {#imap}
The very first section of the configuration is the **IMAP** section.
```conf
IMAPAccount Personal
Host email.hostname.com
User personal@email.hostname.com
Pass "yourPassword"
# One can use a command which returns the password
In here, we configure the **IMAP** settings. Most notably here is of course `Host`, `User` and `Pass/PassCmd`. These settings refer to your server and you should populate them with that information.
The `IMAPStore` is used further in the configuration, this gives a name for the **IMAP**_Store_. In simple terms, if you want to refer to your _server_ you use `personal-remote`.
### Maildir {#maildir}
The next section of the configuration is the **Maildir** part. You can think of this as where do you want _your emails_ to be saved _on disk_.
```conf
MaildirStore personal-local
Subfolders Verbatim
Path ~/.mail/
Inbox ~/.mail/Inbox
```
This should be self explanatory but I'd like to point out the `MaildirStore` key. This refers to _email_ on _disk_. So, if you want to refer to your _emails on disk_ you use `personal-local`.
At this point, you are thinking to yourself what the hell does that mean ? What is this dude talking about ! Don't worry, I got you.
### Synchronize to your taste {#synchronize-to-your-taste}
This is where all what you've learned comes together. The fun part ! The part where you get to choose how you want to do things.
Here's what I want. I want to _synchronize_ my _server_**Inbox** with my _on disk_**Inbox** both ways. If the **Inbox** folder does not exist _on disk_, create it. The name of the **Inbox** on the server is `Inbox`.
This can be translated to the following.
```conf
Channel sync-personal-inbox
Master :personal-remote:"Inbox"
Slave :personal-local:Inbox
Create Slave
SyncState *
CopyArrivalDate yes
```
I want to do the same with `Archive` and `Sent`.
```conf
Channel sync-personal-archive
Master :personal-remote:"Archive"
Slave :personal-local:Archive
Create Slave
SyncState *
CopyArrivalDate yes
Channel sync-personal-sent
Master :personal-remote:"Sent"
Slave :personal-local:Sent
Create Slave
SyncState *
CopyArrivalDate yes
```
At this point, I still have my _trash_. The _trash_ on the server is called `Junk` but I want it to be `Trash` on disk. I can do that easily as follows.
```conf
Channel sync-personal-trash
Master :personal-remote:"Junk"
Slave :personal-local:Trash
Create Slave
SyncState *
CopyArrivalDate yes
```
I choose to _synchronize_ my _emails_ both ways. If you prefer, for example, not to download the _sent_ emails and only _synchronize_ them up to the server, you can do that with `SyncState`. Check the `mbsync` manual pages.
### Tie the knot {#tie-the-knot}
At the end, add all the channel names configured above under the save _Group_ with the same account name.
```conf
Group Personal
Channel sync-personal-inbox
Channel sync-personal-archive
Channel sync-personal-sent
Channel sync-personal-trash
```
## Conclusion {#conclusion}
This is pretty much it. It is that simple. This is how I synchronize my email. How do you ?
