[Info-vax] SMTP chunk sizes

[glen herrmannsfeldt]

Rich Jordan <jordan at ccs4vms.com> wrote:

(snip)

> 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.  If it did then the very slow ACK 
> times would not matter.  So the current situation takes many 
> minutes to send a 6-8MB file and somewhere in that range, 
> takes too long to send and Office 365 sends a 421 error and 
> drops the connection.  

I don't understand chunk size. TCP will put the stream data into
packets, normally not related to the way the program wrote it out.

If the program is writing lines slow enough that TCP decides to
send each before the next comes along, I could see a problem.

Otherwise, you might try a local relay which would accept from 
VMS and then send on its way.  Especially as many don't accept
port 25 mail anymore.  The relay could use one of the newer ports.

-- glen