Mail.app being blocked?

In 48 hours I've sent several emails to two friends with two ISPs. None has gone through.

Mail I send to myself comes through. Three messages I've sent to my yahoo account have, after a period of hours, ended up in the Bulk Mail folder, indicating that Yahoo has identified them as spam.

Of those three, my name is missing from the return address of one, and it has been flagged as having an attachment.

For weeks, a correspondent has reported that my email often comes flagged as having an attachment although I sent no attachment. I don't know if that's related to the current problem.

Could Mail.app be doing something that causes mail servers to identify my messages as spam?
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Relevant Pages

  • Re: HELP!! Dual monitors - Primary shuts off when mouse moves off it!
    ... > first year and each of these guys sells your emails to two more people. ... > you have 26 email addresses sold at the start. ... I suggest you get a spam filter. ... they will be cut off from their ISPs or their ISPs will charge them extra ...
    (alt.linux)
  • RE: OMA and Outgoing Spam
    ... Someone hacked a user account and use it to spam emails; ... Your Exchange server is open relaying emails;(You have checked it ... Your server is under RNDR Attack. ... Microsoft is providing this information as a convenience to you. ...
    (microsoft.public.windows.server.sbs)
  • Re: A flood of spams - another virus on the way?
    ... You would need to totally redesign TCPIP and SMTP with security in mind. ... You can block viruses at the mailhub level the problem is what you then do. ... Spam is a worse problem. ... >number of emails they will be sending out in any one day. ...
    (comp.os.vms)
  • Re: Exchange Weird Issue
    ... Emails are from different external users, ... involved in a conversation with the intended recipient. ... So I don't think it's a spam or open relay issue... ... Your server is open relaying emails. ...
    (microsoft.public.windows.server.sbs)
  • Re: OT: Emailing Quentin
    ... to emails he had sent yesterday. ... first email tagging it as spam on a day when I had a heap of spam. ... Incredimail is notorious for the amount of garbage each email carries. ... Comcast certainly does. ...
    (alt.support.diabetes)