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📄️ Queues

Queues are essentially a holding area for outbound messages in an SMTP server. When a message arrives, it is placed in the queue until it can be delivered to its final destination. Stalwart SMTP supports an unlimited number of virtual queues, which means that a system administrator can create and configure multiple queues with different settings and behaviors. This allows for a high degree of flexibility and customization in managing incoming messages. For example, different queues can be created for different types of messages, such as messages from high-priority senders or messages with specific content, and these queues can be processed differently, such as by assigning more resources or prioritizing delivery.

📄️ TLS security

Stalwart SMTP supports various security measures for secure email transmission, including DANE (DNS-Based Authentication of Named Entities), MTA-STS (Mail Transfer Agent Strict Transport Security) and TLS Reporting. DANE allows for secure authentication of mail servers using cryptographic certificates stored in the domain name system. MTA-STS enforces the use of encrypted connections between mail servers and requires that the recipient's mail server supports encryption. TLS Reporting helps organizations monitor the encryption status of their email delivery, providing information on whether messages are encrypted or not and if encryption is being used, what type of encryption is in use. These security measures aim to increase the privacy and security of email communications and prevent unauthorized access to sensitive information.

📄️ Quotas

Quotas allows to set limits on the message queue to control its size and total number of messages. Stalwart SMTP supports enforcing dynamic quotas on the message queue, which means that it can limit the total size and number of messages waiting to be delivered based on multiple variables. If a queue quota is exceeded, messages will be temporarily rejected with a 4xx SMTP code. This is useful in preventing the server from becoming overwhelmed by too many messages and ensuring that important messages are delivered promptly.