SmtpMail.Send - First Call is very slow

[An2]

I have created vb.net dll which sends emails using SmtpMail.Send method.
I am using the same dll in two exe projects lets call them projSlow and projfast. For projSlow - the first call to SmtpMail.Send takes about 12 seconds the next call takes less then 1 sec, in projefast I don't see any preformance issues all calls take less then 1 sec. Both projSlow and projFast are executed on same machine windows 2000.

Why is call to SmtpMail.Send slow in projSlow?

[Plater]

Do you always execute projslow before projfast?
It could be that the first call does some work that gets cached locally (like a DNS name lookup or something) and any calls made after use the cached values?

[An2]

Do you always execute projslow before projfast?
It could be that the first call does some work that gets cached locally (like a DNS name lookup or something) and any calls made after use the cached values?

No - I did test for that. Even if I ececute projslow 4 or 5 times and lets say there are 2 SMTPMail.Send calls in the projslow, the first call is always slow.
I have been testing all day, can't figure out what can be wrong.

This is what shows in the log file for the two calls:
#Fields: date time cs-method time-taken
2007-12-21 18:22:40 HELO 0
2007-12-21 18:22:40 MAIL 0
2007-12-21 18:22:40 RCPT 0
2007-12-21 18:22:40 RCPT 0
2007-12-21 18:22:40 RCPT 0
2007-12-21 18:22:40 DATA 94
2007-12-21 18:22:40 QUIT 0
2007-12-21 18:22:40 HELO 0
2007-12-21 18:22:40 MAIL 0
2007-12-21 18:22:40 RCPT 0
2007-12-21 18:22:40 DATA 172
2007-12-21 18:22:40 QUIT 0


I recorded the time before and after the SMTP send call - for first call in projSlow it takes 14.0001792 and sec call in projSlow it takes 0.1875024.

The log file does not seem to show that it takes 14.0001792 sec in the first call. Not sure where time is spend when SMTP.Send is called

[Plater]

The first call has 3 people the email is being sent to, perhaps the mail server is taking longer to sort out if the rcpt name is valid or not?
Seems like a very long time though.

[An2]

The first call has 3 people the email is being sent to, perhaps the mail server is taking longer to sort out if the rcpt name is valid or not?
Seems like a very long time though.

If commented out the first call in projSlow and just ran the second call - that also took around 14 seconds

[Plater]

Very strange.
Are both projects talking to the same mail server?

[An2]

Very strange.
Are both projects talking to the same mail server?

Yes they are I am all out ideas - not sure what to try

[Plater]

Yes they are I am all out ideas - not sure what to try

I have never been happy with Microsoft's SMTPClient implementation in .NET, unfortunatly there was never a good alternative that I could find.

In project slow, if you made the 2nd call first and the 1st call second, what is the result?

Such as previously:
Call A (slow)
Call B (fast)

If you swap them:
Call B (slow?)
Call A (fast?)

[An2]

I have never been happy with Microsoft's SMTPClient implementation in .NET, unfortunatly there was never a good alternative that I could find.

In project slow, if you made the 2nd call first and the 1st call second, what is the result?

Such as previously:
Call A (slow)
Call B (fast)

If you swap them:
Call B (slow?)
Call A (fast?)

What I did was comment out the CALL A and just left Call B - then CAll B took about 14 seconds to run

[Plater]

That really sounds like there is caching involved somewhere. (Not sure why)
I guess you could try looking up chaching and the SMTPMail.Send() to see if anyone else has said anything about it?