HTTP Compression

RustMailer supports built-in HTTP compression and decompression using the Poem web framework. This helps reduce bandwidth usage and improve API performance, especially for large JSON payloads or webhook traffic.

✅ Overview

RustMailer automatically selects compression and decompression algorithms based on HTTP headers:

• Request Decompression: If the request contains a Content-Encoding header, RustMailer will decompress it accordingly.
• Response Compression: If the request includes an Accept-Encoding header, RustMailer will choose the best supported compression algorithm.

🛠️ How to Enable

You can enable HTTP compression via command-line argument or environment variable:

Command-line Argument	Environment Variable	Default	Description
--rustmailer-http-compression-enabled	RUSTMAILER_HTTP_COMPRESSION_ENABLED	false	Enables HTTP compression and decoding

Example: Enable via Command Line

./rustmailer --rustmailer-http-compression-enabled

Example: Enable via Environment Variable

export RUSTMAILER_HTTP_COMPRESSION_ENABLED=true
./rustmailer

🔄 Supported Compression Algorithms

RustMailer supports the following compression types:

• gzip
• deflate
• br (Brotli)
• zstd
• * (wildcard - auto-select best available)

Sample Headers

Accept-Encoding: br, gzip, deflate
Content-Encoding: gzip

💡 Use Cases

• High-throughput webhook traffic
• Mobile or bandwidth-constrained environments
• Large JSON API responses
• Uploading IMAP sync data efficiently

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🧬 gRPC Compression

RustMailer also supports gRPC compression, which is configured differently from HTTP compression.

Unlike HTTP compression, where the algorithm is negotiated via headers, gRPC compression requires explicitly specifying the compression algorithm.

🧩 Configuration

Use either a command-line argument or environment variable:

Command-line Argument	Environment Variable	Default	Description
--rustmailer-grpc-compression	RUSTMAILER_GRPC_COMPRESSION	none	Sets gRPC compression algorithm (see below)

🔧 Supported gRPC Compression Algorithms

You must specify one of the following compression algorithms:

none
gzip
brotli
zstd
deflate

⚙️ Example

./rustmailer --rustmailer-grpc-compression=gzip
# or
export RUSTMAILER_GRPC_COMPRESSION=gzip
./rustmailer

🔁 Client Configuration

RustMailer will apply the selected algorithm for both:

• send_compressed(...) (outbound gRPC responses)
• accept_compressed(...) (inbound gRPC requests)

gRPC Client Configuration

The gRPC client must know which compression algorithm is configured on the server, and must set both send_compressed and accept_compressed accordingly.
Mismatched compression settings may lead to connection errors or failed decoding.

For example, when using a gRPC client library (e.g., tonic), configure compression to match:

use tonic::transport::Channel;

let channel = Channel::from_static("http://localhost:16630")
    .connect()
    .await?
    .send_compressed(tonic::codec::CompressionEncoding::Gzip)
    .accept_compressed(tonic::codec::CompressionEncoding::Gzip);

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