Begin by logging into your Mailjet account. Navigate to the "Statistics" section and select the data you wish to export, such as campaign statistics or email lists. Use the export functionality provided by Mailjet to download the data in a CSV or JSON format, which are commonly supported formats for exporting data.

Once you have your data exported, review the file to ensure it contains all necessary fields for your analysis or reporting needs. Open the CSV or JSON file using a text editor or a spreadsheet application like Excel or Google Sheets. Check for consistency, correct any errors, and ensure that the data is clean and ready for transformation.

To interact with your ClickHouse database, you need the ClickHouse client. Install it on your local machine or server by following the official installation guide for your operating system. For instance, on a Linux system, you can install it using the package manager with a command like `sudo apt-get install clickhouse-client`.

Access your ClickHouse server using the ClickHouse client. You will need to create a table that matches the structure of your Mailjet data. Use a SQL `CREATE TABLE` statement to define the schema, ensuring that columns match the data types of your exported file. For example:

```sql
CREATE TABLE mailjet_data (
id UInt32,
email String,
status String,
open_rate Float32
) ENGINE = MergeTree() ORDER BY id;
```

Transform your CSV or JSON data into a format suitable for ClickHouse insertion. This involves ensuring that the data types in your file match those defined in your ClickHouse table. If necessary, convert date formats, escape special characters, or adjust numeric representations in your data file using a scripting language like Python or a command-line tool like awk.

Use the ClickHouse client to load the transformed data into your ClickHouse table. For a CSV file, you can use the `clickhouse-client` command with the `--query` and `--format` options to insert the data:

```bash
clickhouse-client --query="INSERT INTO mailjet_data FORMAT CSV" < path/to/your/transformed_data.csv
```

For JSON, adjust the `FORMAT` clause to `JSONEachRow` or another appropriate JSON format supported by ClickHouse.

After loading the data, verify that the data has been correctly imported into ClickHouse. Run queries using the ClickHouse client to check the count of records, sample entries, or specific fields to ensure that the data in ClickHouse matches what was exported from Mailjet. This ensures that the transfer process was successful and that no data was lost or corrupted.

By following these steps, you can effectively move data from Mailjet Mail to ClickHouse without relying on third-party connectors or integrations.