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    N900 port forwarding for eMail - when port 25 blocked by ISP ?

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    hans51 | # 1 | 2010-05-26, 10:27 | Report

    In the Philippines the largest mobile ISP/mobile network Smart - blocks port 25, thus making sending of eMail from the N900 impossible via my own mail-server.

    For my laptop connections I bypass this port 25 block successfully by port forwarding in bash:

    ssh -L 44999:localhost:25 root@xxx.xxx.xxx.xxx
    and the mail client thus has an smtp server
    localhost:44999

    is there a way to use port forwarding for eMail on a N900 and is there a localhost MTA on a N900 to accept and forward such mails ??

    of course there might be third party mail accounts
    BUT I have a strict SPF record set for my mail servers to ONLY have my own clean IP addresses as used sender IPs. I love to keep my SPF record that strict.

    Any help apreciated

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    uTMY | # 2 | 2010-05-26, 10:30 | Report

    Originally Posted by hans51 View Post
    In the Philippines the largest mobile ISP/mobile network Smart - blocks port 25, thus making sending of eMail from the N900 impossible via my own mail-server.

    For my laptop connections I bypass this port 25 block successfully by port forwarding in bash:

    ssh -L 44999:localhost:25 root@xxx.xxx.xxx.xxx
    and the mail client thus has an smtp server
    localhost:44999

    is there a way to use port forwarding for eMail on a N900 and is there a localhost MTA on a N900 to accept and forward such mails ??

    of course there might be third party mail accounts
    BUT I have a strict SPF record set for my mail servers to ONLY have my own clean IP addresses as used sender IPs. I love to keep my SPF record that strict.

    Any help apreciated
    Hi

    Use OpenVPN to create a tunnel between the N900 and your SMTP server on any port you choose to forward through your home router.

    Then you can use local addressing and port 25 as you like over the tunnel.

    This has the added advantage of not exposing your mail server to potentially erroneous mail relay configuration issues.

    rgds

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    Alan_Peery | # 3 | 2010-05-26, 11:15 | Report

    Originally Posted by hans51 View Post
    In the Philippines the largest mobile ISP/mobile network Smart - blocks port 25, thus making sending of eMail from the N900 impossible via my own mail-server.
    Do they also block the SSL or TLS encrypted ports for SMTP? You may be able to configure your email server to accept thos connections (if it doesn't already) and then have the N900 connect there.

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    jazzmadrazz | # 4 | 2010-05-26, 11:26 | Report

    There's also a tool called "portfwd" (which does precisely what it says...) - check here : http://portfwd.sourceforge.net/

    Originally Posted by hans51 View Post
    In the Philippines the largest mobile ISP/mobile network Smart - blocks port 25, thus making sending of eMail from the N900 impossible via my own mail-server.

    For my laptop connections I bypass this port 25 block successfully by port forwarding in bash:

    ssh -L 44999:localhost:25 root@xxx.xxx.xxx.xxx
    and the mail client thus has an smtp server
    localhost:44999

    is there a way to use port forwarding for eMail on a N900 and is there a localhost MTA on a N900 to accept and forward such mails ??

    of course there might be third party mail accounts
    BUT I have a strict SPF record set for my mail servers to ONLY have my own clean IP addresses as used sender IPs. I love to keep my SPF record that strict.

    Any help apreciated

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    breakd0wn | # 5 | 2010-05-26, 11:29 | Report

    Just configure your mail server to listen on an additional port.

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    hans51 | # 6 | 2010-05-27, 17:13 | Report

    the built in mail client does apparently NOT allow
    localhost
    as mail server
    which makes a common portforwarding mail server for outgoing mail like in my laptop ...

    localhost:44999
    impossible so far

    maybe I need to install additional packages to enable localhost as valid email server ??

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    hans51 | # 7 | 2010-05-27, 22:55 | Report

    Hi guys
    thanks for the help so far
    but

    1.
    the portforwarding part is NO problem - it works with above line on the N900 as it works on my laptop

    the remaining problem is getting mail OUT

    localhost may have NO mail agent to handle mail locally for forwarding

    2.
    I tried repeatedly to change various ports on my mail server
    among others also rfc alternate port 587
    and a few others

    i walked through a complete telnet smtp session on my laptop successfully using alternate port

    but on my N900 it seems that the provider blocks just anything related to outgoing mail independent of port
    on the mail server there are NO error message at all when attempting to send mail from N900

    and of course the receiving of mail works perfectly from N900

    personally when comparing alternate port to portforwarding using a secure tunnel. I prefer ssh portforwarding as in my laptop to ensure nothing is sent clear text.

    so maybe I have to install postfix or something comparable on my N900 to send locally and use pfwd ?
    anyone experience in such procedure with N900 ?

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    uTMY | # 8 | 2010-05-28, 08:46 | Report

    Once again may I suggest having a look at OpenVPN.

    Once you have a tunnel through to your mailserver on any port you choose so it should not get blocked by your ISP.

    You will have access to the local IP address of the mail server (the other end of the tunnel).

    you can then use

    mailserver.vpntunnel.ip.address:25

    from the N900

    All you need then is to tell the mailserver to allow relay from the vpn tunnel address range.

    rgds

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    ruskie | # 9 | 2010-05-28, 11:32 | Report

    Try using telnet on the n900 and walk through the smtp session that way.

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    uTMY | # 10 | 2010-05-28, 12:40 | Report

    Originally Posted by ruskie View Post
    Try using telnet on the n900 and walk through the smtp session that way.
    But that will only confirm to him whether port 25 is open or not.

    instructions

    telnet ipaddress 25
    EHLO

    should elicit a response from the mail server.

    rgds

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