This could get long but will try to keep as short as possible.

Situation:
Our broadband line went down as in No Line tone at all and could be up to 2 days to fix by BT's estimate. This causes major problems with our large busy shop - visa machines, doing finance without broadband and importantly no incoming email.

Here's what I ended up doing:
Found that you could connect a MiFi unit via WiFi with the 2860n which luckily I had one in the car, this was very simple to setup and got broadband for the services the shop needed immediatly, visa machines and iPads could connect to internet to do finance applications and social media. Brilliant feature of the 2860n a lot easier than finding something compatible to plug into the USB slot.

The Mifi is a TP-Link M7350(UN) Mifi with an O2 pay-as-go sim.

The only issue left:
We can send email via our exchange but can't receive even though I have done the following:

2. Made sure port 25 is open on WAN2 to the Exchange Server


4. Have a dyamic DNS setup


6. Dynamic DNS Name set as second mx record

Syslog show no blocking for port 25 or any traffic being permitted so it looks like either the Mifi is blocking it or O2 are blocking incoming port 25.

As far as I can see I Have setup the 2860n correctly, so could it be O2 are blocking incoming port 25, any way to verify? Is there a way round it?

Thanks
John.

I find port 25 is blocked sometimes when travelling. In those cases port 2525 works, might be worth a try? But isn't port 25 your outgoing port and you say you can send emails?

How do you get it connect to the mifi unit?

See here

http://www.draytek.co.uk/support/guides/kb-wan-wireless?highlight=WyJ3aXJlbGVzcyIsIid3aXJlbGVzcyIsIid3aXJlbGVzcycsIiwiY29ubmVjdGlvbiIsImNvbm5lY3Rpb24nLCIsImNvbm5lY3Rpb24nIiwiY29ubmVjdGlvbidzIiwid2lyZWxlc3MgY29ubmVjdGlvbiJd

I assume inbound email is delivered by SMTP on port 25. If so you'll need a real world IP address.
When using O2 on a MiFi (or a dongle) you will only receive a 10.x.x.x IP address from O2. I experienced this when using a 4G dongle on O2 as a backup to BT. So when you update your IP address using DDNS it will receive a 10.x.x.x address which is no good. As you may know 10.x.x.x addresses are not inbound accessible as they are reserved IP addresses (like 192.168.x.x are).

So your only options are to use a mobile provider who gives you a real world IP address or access your email via another means until your phone line is repaired.

Have a look at https://en.wikipedia.org/wiki/Carrier-grade_NAT for details on carrier grade NAT.

Piste Basher wrote: I find port 25 is blocked sometimes when travelling. In those cases port 2525 works, might be worth a try? But isn't port 25 your outgoing port and you say you can send emails?

I will give that port a go as a longshot, will have to tell the Draytek to Pass port 2525 to internal port 25 which should be no issue. Broadband is back up seems some noodle of a BT engineer cut the wrong cables to disconnect someone in one of the cabinets between us and the exchange!