46 lines
1.9 KiB
Plaintext
46 lines
1.9 KiB
Plaintext
MBOX-Line: From imap at tlinx.org Sun Aug 7 18:40:13 2005
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To: imap-protocol@u.washington.edu
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From: Linda Walsh <imap@tlinx.org>
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Date: Fri Jun 8 12:34:36 2018
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Subject: [Imap-protocol] Protocol Q: IMAP(s) svr (want tcp)-> IMAP client
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Message-ID: <42F6B7FD.2000408@tlinx.org>
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Under what circumstances, or why would an IMAP(s) server try to
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open a connection back to a client?
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I currently have firewall rules setup to allow outgoing connections
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from my clients to an external imaps (secure) server. This seems
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to work just fine, but I'm wondering if I am creating some inefficiency
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in downloading IMAPS email.
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I notice (have for a long time) entries in my firewall' "denied"
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traffic log that my ISP's imap server is attempting to initiate
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an inbound TCP connection from server port 993 to a high numbered
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(>50000) client port.
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I'm wondering under what circumstances an IMAP server might try
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to open a new secure connection back to a client server. I don't
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know what server they are using, but I am using fetchmail as a
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daemon running in poll mode using idle. Why doesn't send it
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back on the already open connection?
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I've been hesitant to allow incoming requests do to the increased
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possibility of 'spoofing'. I'm not even sure what process on my
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end should even be "listening" for such a request. I am unsure about
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what credentials it would try to use, though, presumably (?) the
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credentials I used to connect to it? But I don't know that 'fetchmail'
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is even configurable to listen to 'random' ports coming from semi-random
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mail servers (mail1, mail2...mail25, mail26...).
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I've never seen the u.washington IMAP server try to connect back
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to any of the clients I use with it -- and I would an immediate
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popup notification if my imap server tried to open an IMAP connection
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to the client (as my client system is setup to notify me of
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non-whitelisted traffic).
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Thanks for any insight...
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Linda
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