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Only on Outbound emails I get the following error.  Just started yesterday.  I've checked all the settings, etc. and everything is right.  Can't figure it out.  Can anybody help?

An error occurred while sending mail. The mail server responded:  5.2.0 3Ton1x0010PnBoL01TonSu internal error. Please check the message and try again.


All Replies
  • Posted by CarolLM
    28 Jan 2018 2:42 PM

    Hi, please review this link: to see if that corrects your issue.  If it doesn't, send us a message on Facebook, Twitter or email us at for additional assistance.  We're here to help!  Thanks, 

    Carol - Cox Support Forums Moderator

  • Posted by TinaV
    28 Jan 2018 5:18 PM

    CarolLM - I did that already.  I read and did everything I can think of.  My settings are okay and I can send thru gmail.  But if I try to send to a large number of people using my Cox email it won't send and I get that server error message each time.  I used to be able to do this and now can't.  It's not my email client if I can send thru gmail.  It's a problem with Cox.

    Any other suggestions?

  • Posted by jannymv
    28 Jan 2018 7:27 PM

    I have the same problem. "Brian from Cox" had a post on this and I did everything the post stated - on Changing your e-mail server settings for Microsoft Outlook 2007-2016 (I have 2007) and it worked one time. After that it started giving me an error message that "Relaying not allowed" to any recipient.  After several more tries it gives me an error message of "too many bad command" - it also gave me message one other time to the effect that the sever does not accept encrypted messages. This all started when cox made a change to the encryption settings. Is there any plan to fix this? 

  • Posted by John2222
    28 Jan 2018 8:26 PM

    I have the same problem.  I called Cox support today and after searching for awhile, the technician confirmed internal documentation that Cox now has a email sending limit of LESS THAN 10 email recipients.  Otherwise you get that error message.  This is all new within the last week.

    Cox, how about changing that error message to something informative such as "Error.  maximum of 9 email recipients allowed."

    Of course this is ridiculous.  Users can't send out emails to nearby neighbors, boy scout members, church choir members, etc.  How would Cox even send emails to their own tech support department employees?  I'm sure there are more than 9!

  • Posted by Becky
    29 Jan 2018 6:32 AM
    Cox has sending limits in place for outbound email. These limits are intended to reduce the amount of unwanted spam on the Internet by identifying and containing “spam bot” attacks generated from Cox customers’ PCs. These limits are set very high, and it is unlikely that normal residential mailings will surpass the limits. Cox has chosen sending limits based on other ISP’s best practices and analysis of existing email traffic to insure even large legitimate residential mailings complete with no errors.

    Please resend your message using Cox Webmail instead of your current email utility ( I successfully sent an email to 10 recipients this morning using my Cox Webmail account.

    Becky K.
    Cox Support Forums Moderator

  • Posted by TinaV
    29 Jan 2018 8:09 AM

    This is utterly ridiculous!  Limiting emails to 10 addressees is not feasible.  I run a sports organization and am on the board of another organization and routinely send group/mass emails to coaches, staff, families, etc. and addressees are anywhere from 5 to over 200 people.  I've always been able to do this until a few days ago!

    Nice that Cox doesn't even inform people of changes.  Reinforces my strong dislike of Cox - from their cable services to now email.  Need to start looking for another provider.  Almost all my friends no longer use Cox.  Now I know why.

    There has to be a resolution to this.


  • Posted by TinaV
    29 Jan 2018 8:13 AM

    Becky - Insane!  Completely understand spam controls, etc. but a lot of people routinely send to large groups of people for legitimate reasons.  For example - I run a youth sports organization that has over 250 kids and over 75 coaches.  I routinely send emails to those families and coaches. 

    Sending by Webmail is not great as you have to type in each email address and I don't have the time to do that for 200 plus some addresses.  In my email client I can copy a list from an excel file and paste it into the To block in seconds instead of typing each email.

    There has to be a way around this.  Please advise.


  • Posted by John2222
    29 Jan 2018 9:13 AM

    Becky, please check with Alex (Cox support rep) from Sunday afternoon, look up my ticket and confirm (or not) what he told me about email limits and Cox internal documentation for residential customers now in effect.

    I am using Outlook 2016 (Office 365) with Windows 10.  Every Sunday I send a church announcement to about 30 members.  It's been working fine for years.  Yesterday,  I received the bounce error message " ... 552 5.2.0 ... internal error" for each intended recipient.  

    During my own testing I reduced the email to 15 email recipients  (same error), then 10 (same error) and then finally 9 (no error).  Finally I broke the message into multiple "groups" of 9 each and succeeded in sending my original 30 members the email.

    My security settings are correct and match Cox's recent changes.

    It's not realistic to require customers to use your online Webmail app or export all my address book to it.  Outlook 2016 is widely used and respected email "utility" with many features.

  • Posted by jannymv
    29 Jan 2018 9:24 AM

    I agree wholeheartedly - as of now I can't even log on to the outgoing e-mail server - even though all my settings match what Cox says - they're answer to use their webmail is absolutely ridiculous.

  • Posted by jannymv
    29 Jan 2018 9:25 AM

    What an absolutely ridiculous reply from Cox!

  • Posted by TinaV
    29 Jan 2018 12:10 PM

    John - Very well said!  Ridiculous to have them just say to use their Webmail instead of our own email clients that we prefer and have been using.

    What you had to do is ridiculous.  I did think of that, but I routinely send a group email to over 200 families and even breaking my list down to 9"s still would take a long while when previously I did it in a couple of minutes with one email.


  • Posted by AlChub
    30 Jan 2018 1:21 AM

    I just finished talking to Cox tier 2 support -- 9 seems to be the limit for now -- but the helpful person I talked to felt that, once all Cox email users get switched over to SSL, the limit may be raised. Meantime, let's be civil and work with Cox. It's not productive to be limited to 9 recipients, I know, but I suggest patience. Good night from Las Vegas.

  • Posted by TinaV
    30 Jan 2018 8:51 AM

    Agree on being civil, but it is difficult when Cox doesn't even notify anybody on this huge change.  And how much patience should we have before just dumping Cox and trying to find another provider?

  • Posted by John2222
    30 Jan 2018 10:24 AM

    Thanks AIChub for another confirmation from Cox that the new email sending restriction is less than 10 email recipients.  So far no response from any of the forum Moderators, but hopefully we'll get a fix soon!

  • Posted by ksdalet
    31 Jan 2018 9:54 AM

    If COX cannot find a way to fix it, then it is time for a new email client.  Possibly a new ISP.