[Info-vax] SMTP chunk sizes

[Rich Jordan]

On Monday, March 23, 2015 at 11:51:51 AM UTC-5, Stephen Hoffman wrote:
> On 2015-03-23 16:32:01 +0000, Rich Jordan said:
> 
> >      the MS size limit is 25MB; the files being sent are smaller but 
> > hit the connection time limit.
> > 
> >      The firewall indicate the packets going out were
> > 
> >      The ISP provided relay host is 'always busy, retry later', meaning 
> > I think its greylisting the MTAs that use it, which VMS also doesn't 
> > like.
> 
> Greylisting is typically skipped after some specified number of 
> successful messages received after retry, or the whitelisting can be 
> manually configured.  VMS works fine with a greylisting server.   That 
> the ISP server is always busy means something else, such as the need to 
> relay via a submission port for the particular mail server, or 
> potentially a configuration error somewhere.  The TCP/IP Services SMTP 
> server lacks the submission port relay capability, though IIRC Process 
> had (has?) an add-on which allowed something like that.   Postfix and 
> most other current servers do have the ability to use an authenticated 
> relay via the submission port.   TCP/IP Services SMTP has many issues 
> in a modern network.  I almost always gateway through a local Postfix 
> server or equivalent, and generally avoid configuring OpenVMS with 
> TCP/IP Services to send directly.
> 
> > Thought about getting hte community edition of Communigate Pro in place 
> > but for now we're stuck with the hardware/resources we have which means 
> > probably using MS IIS SMTP stack for the smarthost.  Its in test now.
> 
> Using a relay (gateway) through an existing Exchange Server usually works.
> 
> Lamson is Python, and might be convinced to work on OpenVMS, if one of 
> the Process stacks is not an option.
> 
> 
> -- 
> Pure Personal Opinion | HoffmanLabs LLC

Hoff,
     Process is out, for the same reason that PMDF, or an exchange server is out.  Zero budget.

     The ISP relay server is being accessed as documented by them; if its not kicking back the 'busy' errors constantly because its actually busy, I thought it might just greylist everybody on its allow  list (based on IP address; only customer IPs can use it to relay).  However I tried 5, 15, 30, and 60 minute delays and kept getting busy errors so its just not going to work.  The ISP, though they gave me the initial info and assured that unauthenticated access on port 25 would work (I do that from home with some equipment alerts via Comcast), they have not responded since to the trouble reports.

     We have IIS and its SMTP server on a PC box with some resources to spare so that's where we're going for smarthost.

     FYI I just pulled up the trace to O365.  It was my mis-remembering the size of the packets being sent on the outbound emails.  

Outbound packet sizes varied between 834 (780 bytes data) and 444 bytes (390 bytes data) after the first dozen or so.  So its not sending one line at a time; I think I was overlaying the SMTP logs with the traces in my head; it had been a couple of weeks since I reviewed them and sent them to MS support.

Shortest interval to ACK from Microsoft seen was 233ms, average was probably around 250ms, there were frequent 300-320ms intervals.  MS says those longer delays are deliberate.