[Info-vax] SMTP chunk sizes

[Rich Jordan]

On Friday, March 20, 2015 at 3:00:55 PM UTC-5, Stephen Hoffman wrote:
> On 2015-03-20 16:36:22 +0000, Rich Jordan said:
> 
> > We have run into a problem with the sites using VMS as a mail server.  
> > Even the current V5.7 eco 5 (or 4) are having problems sending large 
> > emails to recipients on microsoft Office 365.  So far other services 
> > are not so affected.
> > 
> > The issue seems to be that Office 365 is both very slow acknowledging a 
> > received SMTP record (one line of the file, text ot uuencoded) at 
> > 250-300ms (per our firewall running packet traces), and enforces a 10 
> > minute connection lifetime for any inbound SMTP connection.
> > 
> > They state the problem is the VMS MTA doesn't provide the (I believe 
> > RFC optional) chunk size options and start sending the data in larger 
> > chunks. ...
> > 
> > Currently setting up another box to act as a smarthost...
> 
> That's the easiest way to deal with this, at least in the short term.   
> Gateway (relay) through Postfix or some other mail server.  Adjust your 
> SPF if needed, if you're using that.
> 
> What the Microsoft folks are referring to is ESMTP (EHLO and all), a 
> barrage of RFCs that have been around since ~1995.  AFAIK, VMS with 
> TCP/IP Services knows not of ESMTP, which means no transport-level 
> security, no chunking, no authenticated SMTP, no UTF-8, etc.   You 
> could ask for this enhancement from HP, but I'd suspect it'd only be 
> VSI that might eventually provide it.   This unless somebody ports over 
> OpenSMTPD or some similar software, or gets the Lamson Python mail 
> server working.  There's also the potential to switch over to one of 
> the Process IP stacks.
> 
> There are obviously document-size limits with most mail servers, so 
> there's inevitably a transfer size limit here somewhere.  Some folks 
> use one-time links or other non-SMTP transfer mechanisms, and some 
> clients such as Apple Mail.app with "Maildrop" automate this process.
> 
> 
> -- 
> Pure Personal Opinion | HoffmanLabs LLC

Hoff,
     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.  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.