Changing the imaps port #

Patrick Mahan

22 Jan 2019 22 Jan '19

5:17 a.m.

Dovecot 2.3.4, FreeBSD 11.2

Due to comcast buisness ISP intercepting imaps I need to have my clients connect to non-standard port (9999). Previously I had been using stunnel to receive the imaps connection and forward it to the imap port over 127.0.0.1. But I would like to retire stunnel and have my imap clients connect remotely.

I have configured the imap-login service -

service imap-login { inet_listener imap { address = 127.0.0.1, ::1 port = 143 } inet_listener imaps { port = 9999 } process_min_avail = 3 service_count = 0 vsz_limit = 1 G }

But I am not seeing any listeners on port 9999 -

root@ns(1001)# netstat -an | grep 9999

Using sockstat on FreeBSD:

root@ns(1002)# sockstat | grep dovecot | grep tcp root dovecot 34800 15 tcp4 *:4190 *:* root dovecot 34800 37 tcp4 127.0.0.1:143 *:* root dovecot 34800 38 tcp6 ::1:143 *:*

I have mail_debug = yes, but I don't see any failures. What is the best way to debug why I am not seeing this port number?

Thanks,

Patrick

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＠lbutlr

22 Jan 22 Jan

6:46 a.m.

On 21 Jan 2019, at 20:17, Patrick Mahan plmahan@gmail.com wrote:

...

Due to comcast buisness ISP intercepting imaps

At you sure about that? I've been using comcast business for 7 years and the do not block 143, 993 587 or 25. they do block 110, but that's fine, I stopped supporting POP around 2001.

Other than 110, they block DHCP, NETBIOS, SNMP, and ports 445, 520, and 1080. They will block port 25 on a individual basis, but I've no idea what their criteria is for that.

...

I need to have my clients connect to non-standard port (9999). Previously I had been using stunnel to receive the imaps connection and forward it to the imap port over 127.0.0.1. But I would like to retire stunnel and have my imap clients connect remotely.

An stunnel or a reverse proxy is the best way to do this, honestly.

As for why your config isn't working, my only guess is maybe you need to specify ssl?

inet_listener imaps { port = 999 ssl = yes }

-- If you write the word "monkey" a million times, do you start to think you're Shakespeare? -- Steven Wright

Patrick Mahan

6:58 a.m.

Yes, I am pretty sure about that. I originally was connected via AT&T DSL but wanted the fast access of cable modem. I need permanent IPs which required me to contract with Comcast buisness. Once I switched over, I was no longer able to access my imap server, which was as I mentioned, stunnel listening on the imaps port and forwarding to dovecot listening on the imap port.

I was getting connection refused on my laptop (thunderbird) email client when I was not at home. I validated that it was not because it was reaching my email server. So who ever was rejecting it, I assumed it was somewhere inside the comcast network. Once I switch to a non-standard port, I was able to connect again.

Re needing to say ssl = yes, I thought that was implied for imaps?

I can go back to stunnel, just thought it was an unnecessary layer.

Thanks,

Patrick

On Mon, Jan 21, 2019 at 8:46 PM @lbutlr kremels@kreme.com wrote:

...

On 21 Jan 2019, at 20:17, Patrick Mahan plmahan@gmail.com wrote:

...
Due to comcast buisness ISP intercepting imaps

At you sure about that? I've been using comcast business for 7 years and the do not block 143, 993 587 or 25. they do block 110, but that's fine, I stopped supporting POP around 2001.

Other than 110, they block DHCP, NETBIOS, SNMP, and ports 445, 520, and 1080. They will block port 25 on a individual basis, but I've no idea what their criteria is for that.

...
I need to have my clients connect to non-standard port (9999). Previously I had been using stunnel to receive the imaps connection and forward it to the imap port over 127.0.0.1. But I would like to retire stunnel and have my imap clients connect remotely.

An stunnel or a reverse proxy is the best way to do this, honestly.

As for why your config isn't working, my only guess is maybe you need to specify ssl?

inet_listener imaps { port = 999 ssl = yes }

?

-- If you write the word "monkey" a million times, do you start to think you're Shakespeare? -- Steven Wright

＠lbutlr

8:30 a.m.

On 21 Jan 2019, at 21:58, Patrick Mahan plmahan@gmail.com wrote:

...

Re needing to say ssl = yes, I thought that was implied for imaps?

I would think so, but all the examples I found in a quick search explicitly set it when changing the port.

Also, unlike regular comcast, I have found the tech support on their business to be pretty decent. I’d call them and find out why 993 is blocked.

-- Badges? We ain't got no badges. We don't need no badges. I don't have to show you any stinking badges.

Michael A. Peters

11:25 a.m.

Comcast DNS servers enforce dnssec, AT&T does not (last I checked). If by chance your zone has DNSSEC enabled but mis-configured then it is possible the domain name you use for the dovecot server is not resolving because of a dnssec validation failure.

I have never heard of comcast or any ISP blocking port 993. That would seem to be a violation of net neutrality rules. I use comcast (consumer, not business) and it does not block 993 (does block 25 but that it should block for dynamic issued addresses)

Look at the domain name used in your e-mail client and make sure it actually resolves. If it does not, check to see if DNSSEC validation is the issue.

On 1/21/19 8:58 PM, Patrick Mahan wrote:

...

Yes, I am pretty sure about that. I originally was connected via AT&T DSL but wanted the fast access of cable modem. I need permanent IPs which required me to contract with Comcast buisness. Once I switched over, I was no longer able to access my imap server, which was as I mentioned, stunnel listening on the imaps port and forwarding to dovecot listening on the imap port.

I was getting connection refused on my laptop (thunderbird) email client when I was not at home. I validated that it was not because it was reaching my email server. So who ever was rejecting it, I assumed it was somewhere inside the comcast network. Once I switch to a non-standard port, I was able to connect again.

Re needing to say ssl = yes, I thought that was implied for imaps?

I can go back to stunnel, just thought it was an unnecessary layer.

Thanks,

Patrick

On Mon, Jan 21, 2019 at 8:46 PM @lbutlr mailto:kremels@kreme.com> wrote:
On 21 Jan 2019, at 20:17, Patrick Mahan <plmahan@gmail.com
<mailto:plmahan@gmail.com>> wrote:
 > Due to comcast buisness ISP intercepting imaps

At you sure about that? I've been using comcast business for 7 years
and the do not block 143, 993 587 or 25. they do block 110, but
that's fine, I stopped supporting POP around 2001.

Other than 110, they block DHCP, NETBIOS, SNMP, and ports 445, 520,
and 1080. They will block port 25 on a individual basis, but I've no
idea what their criteria is for that.

 > I need to have my clients connect to non-standard port (9999). 
Previously I had been using stunnel to receive the imaps connection
and forward it to the imap port over 127.0.0.1.  But I would like to
retire stunnel and have my imap clients connect remotely.

An stunnel or a reverse proxy is the best way to do this, honestly.

As for why your config isn't working, my only guess is maybe you
need to specify ssl?

  inet_listener imaps {
       port = 999
       ssl = yes
    }

?


-- 
If you write the word "monkey" a million times, do you start to
think you're
Shakespeare? -- Steven Wright

Michael A. Peters

11:34 a.m.

Another possible thing, I don't know what the bug is or if it is fixed, but few years ago Thunderbird (on CentOS 7) for me refused to connect to Port 993 or Port 465 if I used a self-signed certificate even though the same certificate worked when using STARTTLS and port 143 and 587. The error wasn't an SSL error, it just would act like it was not connecting.

With CA signed certificates it did work on 993 and 465.

On 1/22/19 1:25 AM, Michael A. Peters wrote:

...

Comcast DNS servers enforce dnssec, AT&T does not (last I checked). If by chance your zone has DNSSEC enabled but mis-configured then it is possible the domain name you use for the dovecot server is not resolving because of a dnssec validation failure.

I have never heard of comcast or any ISP blocking port 993. That would seem to be a violation of net neutrality rules. I use comcast (consumer, not business) and it does not block 993 (does block 25 but that it should block for dynamic issued addresses)

Look at the domain name used in your e-mail client and make sure it actually resolves. If it does not, check to see if DNSSEC validation is the issue.

On 1/21/19 8:58 PM, Patrick Mahan wrote:

...
Yes, I am pretty sure about that. I originally was connected via AT&T DSL but wanted the fast access of cable modem. I need permanent IPs which required me to contract with Comcast buisness. Once I switched over, I was no longer able to access my imap server, which was as I mentioned, stunnel listening on the imaps port and forwarding to dovecot listening on the imap port.

I was getting connection refused on my laptop (thunderbird) email client when I was not at home. I validated that it was not because it was reaching my email server. So who ever was rejecting it, I assumed it was somewhere inside the comcast network. Once I switch to a non-standard port, I was able to connect again.

Re needing to say ssl = yes, I thought that was implied for imaps?

I can go back to stunnel, just thought it was an unnecessary layer.

Thanks,

Patrick

On Mon, Jan 21, 2019 at 8:46 PM @lbutlr mailto:kremels@kreme.com> wrote:

    On 21 Jan 2019, at 20:17, Patrick Mahan mailto:plmahan@gmail.com> wrote: > Due to comcast buisness ISP intercepting imaps

    At you sure about that? I've been using comcast business for 7 years and the do not block 143, 993 587 or 25. they do block 110, but that's fine, I stopped supporting POP around 2001.

    Other than 110, they block DHCP, NETBIOS, SNMP, and ports 445, 520, and 1080. They will block port 25 on a individual basis, but I've no idea what their criteria is for that.

     > I need to have my clients connect to non-standard port (9999). Previously I had been using stunnel to receive the imaps connection and forward it to the imap port over 127.0.0.1. But I would like to retire stunnel and have my imap clients connect remotely.

    An stunnel or a reverse proxy is the best way to do this, honestly.

    As for why your config isn't working, my only guess is maybe you need to specify ssl?

     inet_listener imaps { port = 999 ssl = yes }

    ?

    --     If you write the word "monkey" a million times, do you start to think you're Shakespeare? -- Steven Wright

Odhiambo Washington

8:58 a.m.

On Tue, 22 Jan 2019 at 06:17, Patrick Mahan plmahan@gmail.com wrote:

...

Dovecot 2.3.4, FreeBSD 11.2

Due to comcast buisness ISP intercepting imaps I need to have my clients connect to non-standard port (9999). Previously I had been using stunnel to receive the imaps connection and forward it to the imap port over 127.0.0.1. But I would like to retire stunnel and have my imap clients connect remotely.

I have configured the imap-login service -

service imap-login { inet_listener imap { address = 127.0.0.1, ::1 port = 143 } inet_listener imaps { port = 9999 } process_min_avail = 3 service_count = 0 vsz_limit = 1 G }

But I am not seeing any listeners on port 9999 -

root@ns(1001)# netstat -an | grep 9999

Using sockstat on FreeBSD:

root@ns(1002)# sockstat | grep dovecot | grep tcp root dovecot 34800 15 tcp4 *:4190 *:* root dovecot 34800 37 tcp4 127.0.0.1:143 *:* root dovecot 34800 38 tcp6 ::1:143 *:*

I have mail_debug = yes, but I don't see any failures. What is the best way to debug why I am not seeing this port number?

Thanks,

Patrick

I would leave dovecot config untouched and use a firewall (PF) to translate port 9999 to whatever dovecot listens to.

-- Best regards, Odhiambo WASHINGTON, Nairobi,KE +254 7 3200 0004/+254 7 2274 3223 "Oh, the cruft.", grep ^[^#] :-)

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＠lbutlr
Michael A. Peters
Odhiambo Washington
Patrick Mahan