Prefilter MTA global security policies for incoming emails:

• Maximum message size including attachments: 50MB
• Maximum number of recipients: 1000
• Maximum layers of compression for attachments: 19
• Maximum number of files in compressed attachments: 300

• Delivery retry interval starts from 60 seconds with retry multiplier of 1.5. Therefore, retry interval will increase by half for every delivery attempt. i.e. 60, 90, 135…
• The maximum retry interval is 3600 seconds.
• The maximum time a message stays in the retry queue is 5 days. Before that timeout, the message will be redelivered with retry interval. Afterwards, the message will be removed from the queue and the sender will receive an NDR message.