Formatting email header correctly for multiple TO addresses

sozotech

• September 12, 2023 10:16

I have a customer who has an application sending emails via a cPanel server. For many years they have had no issues sending to GMAIL but recently have been getting this error. 550-5.7.1 This message is not RFC 5322 compliant. There are multiple To headers. 550-5.7.1 To reduce the amount of spam sent to Gmail, this message has been 550-5.7.1 blocked. Please visit 550 5.7.1

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  cPRex Jurassic Moderator

  • September 12, 2023 15:43

  Hey there! Here are the official details from Google, which you have likely already found:

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  sozotech

  • September 12, 2023 17:24

  Hey there! Here are the official details from Google, which you have likely already found:

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  cPRex Jurassic Moderator

  • September 12, 2023 18:25

  At least this confirms the issue is in the application. Is there a way to try it without the space in the application just to be sure? Either way, it seems like this isn't related to cPanel but the way the app is handing over the email list to Exim. It should accept the list and then process each recipient separately.

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  sozotech

  • September 12, 2023 21:06

  At least this confirms the issue is in the application. Is there a way to try it without the space in the application just to be sure? Either way, it seems like this isn't related to cPanel but the way the app is handing over the email list to Exim. It should accept the list and then process each recipient separately.

  
  

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  sozotech

  • September 12, 2023 21:23

  At least this confirms the issue is in the application. Is there a way to try it without the space in the application just to be sure? Either way, it seems like this isn't related to cPanel but the way the app is handing over the email list to Exim. It should accept the list and then process each recipient separately.

  
  I verified via telnetting to port 25 and manually entering in the RCTP TO:, gives this error so I know it is not just the application. I will have to do some more investigation I guess to figure out why this is happening.

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  quietFinn

  • September 13, 2023 11:53

  I verified via telnetting to port 25 and manually entering in the FROM:, gives this error so I know it is not just the application. I will have to do some more investigation I guess to figure out why this is happening.

  
  It's a bit confusing, you tell you are getting various error messages, but you don't (always) tell from where the errors are coming from, i.e is it the local Exim, or the receiving (Gmail?) server. Besides I don't think you can have multiple addresses in FROM

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  sozotech

  • September 13, 2023 13:30

  It's a bit confusing, you tell you are getting various error messages, but you don't (always) tell from where the errors are coming from, i.e is it the local Exim, or the receiving (Gmail?) server. Besides I don't think you can have multiple addresses in FROM

  
  Sorry for the confusion, first off the FROM should have been RCPT TO: and this is the connection to the cPanel server attempting to send to Gmail getting the error. Hopefully I will get more time today to trouble shoot this, I've just not seen this before as to why the server won't accept multiple To recipients. It has to be something wrong with the handshake to the server from their app but just not sure why I get the same error manually inputing the email via telnet.

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