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  1. #1
    Join Date
    Mar 2006
    Johannesburg,South Africa

    advice needed about "554 Too many recipients"

    Hi all,

    A client of ours just requested to increase the max_recipients in Exim to 300, since he keeps getting "554 Too many recipients" error when sending a marketing email from MS Outlook.

    Before you tell me to use Pine / Mutt / etc to send plain-text emails via mailman, this isn't an option.

    I would like to know, what are the implications of increasing the default 100 to 300? If 300 email recipients were added to the "To:" field, does it establish 300 connections to the SMTP server, or not?

    In the Exim documentation ( I found this:

    "If this option is set greater than zero, it specifies the maximum number of original recipients for any message. Additional recipients that are generated by aliasing or forwarding do not count. SMTP messages get a 452 response for all recipients over the limit; earlier recipients are delivered as normal. Non-SMTP messages with too many recipients are failed, and no deliveries are done.

    Note: The RFCs specify that an SMTP server should accept at least 100 RCPT commands in a single message."

    But, this doesn't tell me if it will have a performance issue with the server, or if other mail servers will have problems with our mail server sending the email to so many recipients in one go.

    Can someone give me some pointers on this one?
    South African Web Hosting - || SA WebHostingTalk -

  2. #2
    Join Date
    May 2008
    Citrus Heights, CA
    Marketing Email = Spam?

    Is he providing you a valid reason? If not, just say no. Make them go elsewhere to spam.
    Best Regards,


  3. #3
    Join Date
    Dec 2001
    Toronto, Ontario, Canada

  4. #4
    Join Date
    Mar 2003
    Moved > Technical & Security Issues.
    Specially 4 You
    JoneSolutions.Com ( Jones.Solutions ) is on the net 24/7 providing stable and reliable web hosting solutions and services since 2001

  5. #5
    If 300 email recipients were added to the "To:" field, it won't create 300 connections. It will give just give you those 300 recipients in one SMTP session. The implications of increasing the limit is just that your users can send more email at once.
    Increase email deliverability and know who clicked and opened your emails.

    SendGrid, reliable SMTP service.

  6. #6
    Join Date
    Mar 2009
    Austin Tx
    Your guy is going to start running into mail server rejecting because of to many addresses. 300 CC is extremely large, and quite a horrible way to do things, not to mention if he doesn't at least use BCC: everyone will see each others addresses.
    I would highly recommend requiring him to move to some mailing list software...phplist, etc.

    If this is unsolicited email he is sending, also take into consideration he may get your server blacklisted. I demand any large lists have proof of opt-in myself.
    This is the best signature in the world....Tribute!
    (It is not the best signature in the world, no. This is just a tribute)

  7. #7
    Join Date
    Nov 2006
    I agree with the statements above: ask him to use software or a script that can send in segments rather than all at once.
    A casual blog mainly about the web hosting industry

  8. #8
    If he uses some type of software, it will generate 300 emails which will be more inefficient as opposed to one email with 300 RCTP TOs. I agree with changing CC to BCC but besides that, I don't see why it would be better to send 300 separate emails instead of sending one email with 300 RCPT TOs.
    Increase email deliverability and know who clicked and opened your emails.

    SendGrid, reliable SMTP service.

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