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Error message 554 5.7.1 (P4) Message Blocked due to Spam Content

  • 23 replies
  • 1 has this problem
  • Last reply by ampico-kid

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Thunderbird was working fine for a number of years, and then out of the blue I get this error message when I try to send e-mail: The Mail Server responded 554 5.7.1 (P4) Message Blocked due to Spam Content in the Message.

Nothing has additions or changes to my Thunderbird e-mail. These are one on one e-mails I'm trying to group mailings. My carrier is RCN and I can send e-mail from my RCN webmail address. I can receive mail with no trouble. RCN claims it's not their issue. BUT.....I also have a Samsung Galaxy 7 phone with an ANDROID OS. I get a similar error message on my RCN e-mail account on the phone. Two totally separate devices....different OS....but same problem. I have changed nothing on the phone...heck I can hardly figure out how to answer an incoming call let alone mess around with e-mail settings. I have two other e-mail accounts on the same desk top computer and phone that both work is a Yahoo account, and one is a Verizon account. I'm not a high level tech with these devices...please make suggested remedies as simple as possible. Thanks very much....Bob

Chosen solution

Another option, that might avoid the RCN-rejection issue, is to send from the RCN account, but through the Yahoo smtp. Like with gmail, you add the RCN account as a verified or authorized sending account, so recipients see your messages as sent from RCN, even though they went through a non-RCN smtp. Add the RCN account to Yahoo via Yahoo webmail settings (and receive the validation email), then in TB, select the account in the left pane of Tools/Account Settings, and choose the Yahoo smtp in the Outgoing Server (SMTP) drop-down in the right pane.

Yahoo smtp settings are: on port 465, SSL/TLS, authentication = OAuth2.

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I managed to find the configuration editor and changed "mail.stricly_mime" from false to true. I thought that did the trick, but just got a message back from an e-mail recipient that the question marks are still there. What's the next step? Thanks. Bob


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Not sure if it matters, but did you restart TB after changing the preference?


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Not sure if I restarted TB after changing the preferences. I changed them yesterday and sent the message yesterday. I'll send another test message tonight and see what happens. I'll let you know what happens. Thanks. Bob


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