SMTP Session is closed after each recipient over SSL

ActorMike

Well-known member
Affected version
2.2.13 but also happened in much older versions.
I noticed this a few years ago, but didn't want to fool with it so I just used a non-SSL connection since our mail server and web server are all on one Windows 2019 machine and when the spool messages are sent they go out via TLS anyway. Worth noting, that this issue also presented on a Win 2012 R2 server.

When I put in our secure mail server connection and email users, it does one at a time. When we used a non-secure method, it does them in batches of as many as 100+.

I worked with the support team at SmarterTools and they determined the limitation is within XF for the following reasons after testing our server. This is NOT by opinion, but theirs:

The reason why it's faster on a non-secure connection is because it's not closing the connection it just calls an RST command. This means that it doesn't have to go through the whole SMTP session again. It can just immediately specify the recipients.

This specific issue is happening over SSL in XF because instead of declaring another RCPT TO address XF is starting a whole new session. I'm able to authenticate and declare as many RCPT TO sessions as I like with the Python SMTP lib while going over TLS or SSL encryption. So I think that this has to be a limitation within XF.


This has a crippling effect when trying to email 10,000 users!
 
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