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Email protection: advanced settings

Hi all,

I use Email Protection in a simple way. This is my SMTP relay only.

However, the sending is done via scripts. The scripts generate a large number of connections, therefore the logs contain messages of saturation of set liits.

2023:06:09-10:33:42 <MY_MTA_NAME> exim-in[22546]: 2023-06-09 10:33:42 rejected MAIL command H=(SRV_NAME) [<SRV_IP>]:49594: too many messages in one connection

To what values can I safely increase the limits?
What is the unit of time for limits, e.g.:
Max mails/connection: 1000
Max rcpt/mail:100

per hour/minute?



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  • Hello  ,

    Thank you for reaching out to the community, Max mails/connection:The maximum messages per SMTP connection requires a number in the range 1-65535.
    Max connections/host:The maximum number of concurrent SMTP connections per host requires a number in the range 1-65535.
    Note – If the value is 0 the connection number per host is unlimited.
    Max rcpt/mail:The maximum number of SMTP recipients per mail requires a number in the range 1-65535.
    Max connections:The maximum number of concurrent SMTP connections requires a number in the range 1-65535.
    Max message size: The SMTP proxy maximum message size requires a number in the range 1-999.The maximum message size that is accepted by the proxy. This setting applies to both incoming and outgoing emails. If your backend server has a limitation with regard to message sizes, you should set the same or a lower value here. Default is 50 megabytes. The maximum message size limit is 250 megabytes. Unit is max connection per each mail you send.

    Thanks & Regards,
    _______________________________________________________________

    Vivek Jagad | Team Lead, Global Support & Services 

    Log a Support Case | Sophos Service Guide
    Best Practices – Support Case


    Sophos Community | Product Documentation | Sophos Techvids | SMS
    If a post solves your question please use the 'Verify Answer' button.

  • Thanks for the clarification.

    I understand that it takes values 1-65535 per connection.

    Why am I asking? In the logs, the server establishes a connection:

    2023:06:09-10:14:11 mta03-1 exim-in[11486]: 2023-06-09 10:14:11 SMTP connection from [XX.XX.XX.XX]:49594 (TCP/IP connection count = 1)

    this connection got the ephemeral port value - 49594.
    In establishing the connection, the client system sent out thousands of emails. But at some point, I got lost connection:

    2023:06:09-10:33:42 mta03-1 exim-in[22546]: 2023-06-09 10:33:42 rejected MAIL command H=(<srv_name>) [XX.XX.XX.XX]:49594: too many messages in one connection
    2023:06:09-10:33:42 itcsr1mta03-1 exim-in[22546]: 2023-06-09 10:33:42 SMTP connection from (<srv_name>) [XX.XX.XX.XX]:49594 lost D=19m30s

    From the log, I interpreted that after 19 minutes and 30 seconds, the server has saturated the Max mails value.

    My server sends about 160k emails/flow unfortunately it is generated by the script.

    From what I understand, my MTA will always disconnect the session because the server in this case will always saturate the limit of 65535 emails.

  • Your sending server's limit and capability highly depends !

    Thanks & Regards,
    _______________________________________________________________

    Vivek Jagad | Team Lead, Global Support & Services 

    Log a Support Case | Sophos Service Guide
    Best Practices – Support Case


    Sophos Community | Product Documentation | Sophos Techvids | SMS
    If a post solves your question please use the 'Verify Answer' button.