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634Part VRunning ServersSome remote mail servers may refuse to send messages to you if you are using acertificate that is not signed by a CA that they recognize. If this happens, then youmay need to remove the -o smtpd_use_tls=yesoption from the smtpline. Replace smtpd_enforce_tlswith smtpd_enable_tlson the port 587 line ifyou need to maintain support for non-TLS clients on that port due to packetfilters. 9.Enable SSL/TLS in the Courier-IMAP daemon by editing /etc/courier/ imapd-ssland replacing the values for TLS_CERTFILEand TLS_TRUSTCERTSwith the following: TLS_CERTFILE=/etc/ssl/private/mail.pemTLS_TRUSTCERTS=/etc/ssl/certs/ca-certificates.pem10.Restart Postfix and the Courier-IMAP daemons: # invoke-rc.d postfix restart# invoke-rc.d courier-imap restart# invoke-rc.d courier-imap-ssl restart11.Configure your mail clients to use SSL. All SSL-enabled clients should supportSSL/TLS when sending to port 465 and when receiving on port 993. Newerclients that support the STARTTLS extension should also be able to useSSL/TLS when sending to port 25 or 587, and when receiving from port 143. SummaryUsing Linux and a good Internet connection, you can set up and maintain your ownmail server. Preparing your computer to become a mail server includes configuringyour network connection, setting up delivery and retrieval methods, and addingrequired software packages. This chapter describes how to install, configure, and troubleshoot two of the mostpopular open source server packages: sendmail and Postfix. Those packages canbeused in tandem with spam filtering software (such as SpamAssassin) and virusscanning software (such as ClamAV). Methods for securing your mail server includeconfiguring support for SSL/TLS encryption. … Caution33_
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