Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

"An error occurred while sending mail. The mail server responded: 6.6.0 Error sending message for delivery.. Please check the message and try again."

  • 6 replies
  • 2 have this problem
  • 488 views
  • Last reply by daveteauk

more options

This message appears upon trying to send just one message. Other messages go out fine. The number of recipients is not any greater than for any other message I've sent over the years, and there isn't even an attachment involved. I've checked the list of recipients to ensure that the email nomenclature is correct, and it is. I have saved this message and continue to have no problem with anything else I'm sending. Finally, it says, "Please check the message and try again." I have no idea what I'm supposed to be looking for when I "check the message." It is just text, like any other simple message, with no hidden codes or anything else, assuming I could even insert hidden codes. In many years of using Thunderbird this has never happened before. Maybe it's something simple, like chewing gum and walking backwards at the same time. What can you tell me?

This message appears upon trying to send just one message. Other messages go out fine. The number of recipients is not any greater than for any other message I've sent over the years, and there isn't even an attachment involved. I've checked the list of recipients to ensure that the email nomenclature is correct, and it is. I have saved this message and continue to have no problem with anything else I'm sending. Finally, it says, "Please check the message and try again." I have no idea what I'm supposed to be looking for when I "check the message." It is just text, like any other simple message, with no hidden codes or anything else, assuming I could even insert hidden codes. In many years of using Thunderbird this has never happened before. Maybe it's something simple, like chewing gum and walking backwards at the same time. What can you tell me?

Chosen solution

An error occurred while sending mail. The mail server responded: 6.6.0 Error sending message for delivery.. Please check the message and try again.

I tried adding my email as to and the rest bcc and it worked. This is on a win10 system - my old win7 laptop has no problems.

Read this answer in context 👍 0

All Replies (6)

more options

Well we do have something of a quandary here.

Mail status codes such as you have posted are in the form X.Y.Z

so in your case the 6 value is out of the approved range by the standard for an email error. RFC3463 describes the first digit (The X part )as;

     2.XXX.XXX   Success
        Success specifies that the DSN is reporting a positive delivery
        action.  Detail sub-codes may provide notification of
        transformations required for delivery.
     4.XXX.XXX   Persistent Transient Failure
        A persistent transient failure is one in which the message as
        sent is valid, but persistence of some temporary condition has
        caused abandonment or delay of attempts to send the message.
        If this code accompanies a delivery failure report, sending in
        the future may be successful.
     5.XXX.XXX   Permanent Failure
        A permanent failure is one which is not likely to be resolved
        by resending the message in the current form.  Some change to
        the message or the destination must be made for successful
        delivery.

Your value of 6 is just not defined. So I think we need as much information as you can provider about your provider. Like who it is and what the SMTP server you are using is named.

By inference I am thinking that the 6 is something invented by the sever software authors and may translate to the on forwarding part of the process. But even if that is the case the generic second digit (The Y digit) offers a fairly generic error literal. X.6.XXX Message Content or Media Status

The message content or media status codes report failures involving the content of the message. These codes report failures due to translation, transcoding, or otherwise unsupported message media. Message content or media issues are under the control of both the sender and the receiver, both of which must support a common set of supported content-types.

Hence my request for more information about the provider. While searching I did encounter a reference on a SKY mail forum about the Yahoo policy of not allowing mail without a To entry to send. The error given there is 554 6.6.0 Error sending message for delivery.

Is that your issue perhaps.

more options

1. Because it was the easiest thing to do, I tried entering one "To" address---my own---to the list of sendees (the rest being Bcc). I did not expect this to work, because I have sent countless emails to Bcc recipients only---no "To" recipient---and never, ever had this problem before.

But, this is AT&T/Yahoo, after all, a lash-up that must have been concocted in the Infernal Regions, as Gen. Patton would have put it. Very often when there is a problem, the one points at the other, and the other points back---all most helpful, as you might imagine.

But, for whatever reason, Yahoo (they run the email for AT&T, which is like having Bozo the Clown in charge of neurosurgery, although he at least would be entertaining) I guess decided to stomp on my effort to send another Bcc-recipients-only email without ever in years saying that it was not acceptable.

I do this Bcc business to protect the recipients, not all of whom know everyone else. I don't like my email address thrown around that way, so I try to keep the email addresses protected, too.

I just received the email I sent, which means it worked for sure.

2. The internet provider is AT&T, who lashed up with (blecch) Yahoo for email. I tried "nslookup" in my DOS command prompt and got these results, which I present in case it could have had anything to do with this:

Default Server: homeportal

Address: 2600:1700:a700:7ff0::1

Thank you.

more options

Arvidd's msg. was very pertinent for me because the next day I experienced the same 6.6.0 error thing, with ATT/yahoo mail. But today I was able to send a msg to myself via bcc ( with no "send to" party). And then I wasn't, and then I was. I hope this is only a brief glitch, but I fear it's related to either security filters or surveillance needs

more options

Unfortunately, this seems to be one of the many blessings connected with AT&T/Yahoo email.

more options

Chosen Solution

An error occurred while sending mail. The mail server responded: 6.6.0 Error sending message for delivery.. Please check the message and try again.

I tried adding my email as to and the rest bcc and it worked. This is on a win10 system - my old win7 laptop has no problems.

more options

This is NOT a 'solution' but just a work around. It's good that someone found this workaround, so we can at least send mail by Bcc, but it's not a solution to our problem. The problem happened earlier this year, around March, and was fixed with an update in TBird, but this time we're getting no help from Mozilla/TBird whatsoever. 'SHAME' on you Mozilla. Time to find another email client I reckon.

On another subject - which Moron wrote the code for this 'support' page?? When one want to make some text BOLD, you highlight the text, then press the 'B' button, as you would in ANY other text editor on Earth,, buuut, it DOESN'T change to BOLD, it just gets a series of inverted commas arount it - Doh! Idiots. Update - the inverted commas change to Bold text only when one actally preses 'Post'. Then they become bold!! Weird!

luntronjim said

An error occurred while sending mail. The mail server responded: 6.6.0 Error sending message for delivery.. Please check the message and try again. I tried adding my email as to and the rest bcc and it worked. This is on a win10 system - my old win7 laptop has no problems.

Modified by daveteauk