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Hi there,
Is there a limit to the number of simultaneous connections that can be made to the SendGrid SMTP server(s)? I run a fairly intensive batch job of up to 500k emails that is driven by a set of parallel worker threads that all connect to the SendGrid SMTP server. Right now there are about 10 threads working but I'd like to scale this up.
(I am aware of the ability to send personalized emails to multiple recipients through the SMTP header API. For reasons not worth getting too into my business rules are too hairy to take advantage of this functionality. Great feature, though.)
Doug
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I’m
not panicking
Is there a limit to the number of simultaneous SMTP connections?
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I’m
looking for an answer
From ASPEmail documentation:
Simultaneous Sessions
This number must be between 1 and 64 and defaults to 16. It specifies the number of SMTP sessions EmailAgent opens simultaneously with an SMTP server to send out queued mail.
Tip: While it may be tempting to use all 64 threads, consider the following: if your SMTP server is configured to limit the total number of simultaneous sessions to, say, 20, all extra sessions will be dropped, and the corresponding messages returned to the queue for resending. This will actually slow your system down.
Ask your system administrator how many simultaneous sessions your SMTP server allows, and set this parameter accordingly.
How many simultaneous sessions does SendGrid's SMTP server allow?Comment -
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Hello,
Sorry for the delay in response. We have recently been monitoring this site more heavily.
We recommend using 20 simultaneous connections, with 100 emails in each connection source.
Ryan -
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That's a good recommendation, and happens to match the default concurrency limit for mails servers like Postfix (http://www.postfix.org/TUNING_README..... Is there a *limit* to the number of simultaneous connections that can be made to SendGrid though? 20 is a good recommendation, but business rules make require that a large number of emails are sent as close to a particular time as possible, and bumping the concurrency limit up to, say 50, may help reduce time spent waiting on send queues.
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there isn't a hard limit per user. Use what you need, we'll handle the details. After all, it's "email delivery. simplified.", not "email delivery. as hard as doing it yourself".
That said, more than 200 simultaneous connections would be viewed as excessive from just about all our users, and by 1000 or so, the assumption is you're up to no good. -
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I’m
thankful
Thank you for the excellent answer! I can see how 200+ can be seen as excessive. I just wanted to make sure bumping up to 50 or so wasn't going to cause our account to be flagged or anything.
In the future we may need to ramp that up so it's nice to know we have some room to work with.
Again, thank you - I wasn't expecting an answer so quickly! -
