Re: Gmail and SPF

In comp.misc Chris J Dixon <chris@cdixon.me.uk> wrote:

I use Forte Agent to send email, via Virgin's mail servers, with
replies forwarded via my own domain email address.
 
I have set up the Gmail app password, which has been working
fine, but am now getting bounce messages like this:
 

[...]

but find myself totally unable to understand exactly what to do.
It also seems like trial and error is not a good way to go, if I
correctly understand that updated entries can take up to 48 hours
to propagate.
 
If I send directly from Virgin's online mail page, there are no
issues.

The short answer is that any time you send a message as
anything@yourdomain.com you need to send via the mail server run by the
people who host your domain.  They can ensure that your domain has a
matching SPF record for their server.

The longer answer is that it is technically possible to add an SPF record to
your domain's DNS to indicate which server is a valid sender for
anything@yourdomain.com.  In an ideal world you'd add virgin's server and
that would resolve the problem.  However the IT of big companies is not
simple, and as a general rule we couldn't guarantee how Virgin are going to
route their email internally and where it will emerge.  It is also liable to
change without warning.  So in practice this is just going to store up
problems for the future.

It used to be that you'd send email via the SMTP server of the network your
were on (eg your ISP's server at home and your employer's at work), who had
a whitelist based on IP addresses (all ISP customers could use their
server).  That doesn't work any more: if you have a domain the mail needs to
go via the hoster for the domain so that it emerges matching the domain's
SPF record.  If you do use the 'wrong' server then it's highly likely the
messages will be rejected as spam, as you are seeing.

Theo