INSTRUCTIONS FOR POST OFFICE CUSTOMERS
SMTP delivery of mail:
When SMTP mail is received by our servers we attempt immediate delivery. If
the destination server is offline then the mail is stored in a queue and we attempt
delivery periodically - every 30 mins. SMTP mail is 'pushed' by our server to a
customer's current IP address as provided by their DNS.
With the current implementation of ADSL in Botswana a customer's IP address is dynamic
i.e. it can vary unpredictably. We keep track of an SMTP Post Office customer's IP
address using our own dynamic DNS service branded BTGDynDNS. This not only allows us to
ensure efficient mail delivery but it also facilitates our ability to monitor our Post
Office customers' ADSL line performance and proactively warn them about connectivity
issues. In addition to this it allows us to get an overall picture of how the BTC ADSL
service is running and to identify problem areas.
Using Dial-Up to retrieve mail:
If a customer attaches a modem to their mail server then, when the customer connects, our
BTGDynDNS service will automatically recognise the new IP address and publish it the
customer's public DNS.
If the customer stays online sufficiently long then the mail queue will run and mail will
be delivered to them, however this may mean staying connected for up to 30 mins. To avoid
this delay the customer's mail server should be configured to send an ETRN to our server
to trigger a run of the mail queue.
The same situation can arise if a customer's ADSL is down and is subsequently restored.
We observed that on 17/08/2011 some customers served by BTC's MSU1 exchange had their
connectivity restored at about 23h30 but lost it again at about 23:45. Many of them
didn't receive their mail in that time as they had no ETRN configured.
Having said that here is a caution to over-enthusiastic techies - please don't try to issue too many ETRNs. Too many concurrent threads will eventually cause timeouts and slower mail retrieval.
If you are attempting to install a dialup modem, configure ETRNs or dequeue you mail
over an unstable ADSL link then please contact us. We can monitor your attempts and
Dialup modems have the potential to incur big telephone bills. Please monitor your modem
to avoid nasty month-end surprises.
This page is subject to revision.
Last edited 09:52 18/08/2011
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