On 05-Oct-2012 09:40:58 Chris Green wrote:

As per the subject line, do most SMTP servers (as in systems 'out there' which send me mail) behave reasonably sensibly when my SMTP server is temporarily not functioning?

I currently have both a desktop machine *and* a small server machine which are on all the time. It's the server machine that receives my E-Mail. The only reason I have it configured this way is because I'm more likely to rebuild/reconfigure my desktop machine than the server machine and I felt that keeping my SMTP server online consistently was important.

However I'm wondering if the effort (and cost) of running two systems all the time is worth it. The other functions of the server system (DNS and CUPS) can easily be run on my desktop machine, occasinal downtime of those services is easily explained to other family members! :-)

If real world SMTP servers 'out there' will cope quite happily with my domain's MX machine being AWOL for several hours then I may as well put everything on the one server machine.

(Note it's only *my* E-Mail that is delivered by SMTP, all other family members do their own thing as in use Webmail, or IMAP, or whatever)

-- Chris Green

I think that the short answer is "it depends".

I think most SMTP server which are sending mail will re-try a number of times, with a "re-try interval" between attempts. How many times this is done, and what the re-try interval may be, will vary between servers. So success will depend on how long is "several hours", given the characteristics of the sending server. And ISPs usually have a "farm" of servers, attempts being handed on from server to server, so that can be a factor too.

That said, it is my impression that most servers will re-try from time to time for up to 24 hours (or more).

Of course, if the server fails to send after the due number of re-tries, it will bounce the email back to sender with a delivery-failure message.

(That's about as far as my limited knowledge goes about what goes on "out there").

Brest wishes, Ted.

------------------------------------------------- E-Mail: (Ted Harding) Ted.Harding@wlandres.net Date: 05-Oct-2012 Time: 10:57:07 This message was sent by XFMail -------------------------------------------------

On 05/10/12 10:40, Chris Green wrote:

As per the subject line, do most SMTP servers (as in systems 'out there' which send me mail) behave reasonably sensibly when my SMTP server is temporarily not functioning?

A sensible mail server will behave sensibly, others may not. The mail server I use has a set of preset retry intervals, which work something like this, multiple retries, each retry after a larger time interval, until it expires and is bounced back to the sender - e.g.

Send, retry after 5 mins, 10 mins, 30 mins, 1 hour, 2 hours, 4 hours, 8 hours, 1 day, 2 days, quit. Other mail servers may behave differently, depending on the implementation of the mail server, and the configuration the user may have done. Not all servers will behave the same way.

So if you're relying on other mail servers' behaviour, then when/if you receive your email would depend on if your machine's availability coincided with a retry by the server trying to talk to you.

I wouldn't go down that route - either have a mail server to receive the mail and have it on all the time, or get someone else to handle your mail for you. Your ISP could do it, or Google can do it for you.

If you have someone else doing the mail for you (e.g. Google), you don't have to use webmail, you can probably access the mail from their servers IMAP, or still have a mail server storing the mail locally (but not recieving it via SMTP), and instead use something like FetchMail to fetch your mail from the ISP/Google's mail server when your machine is switched on. Or just do the old thing of host the email at the ISP, then fetch it with an email client (which stores your email) via POP3.

HTH Steve