topic Users unable to access external email servers ASA even with insp in Network Security

Users unable to access external email servers ASA even with inspect esmtp removed

powermann — Mon, 11 Mar 2019 21:55:26 GMT

Hi All. I have a issue that i am at a loss as how to slove it. I have an ASA 5505 as my firewall. I have users from other companies who visit from time to time and are unable to use their outlook email to send messages. They can however receive messages without a problem. I also have a situation where users who use windows live to access gmail are unable to send messages.

I have narrowed it down to the fact that these uses are using ssl/tls to send the mails. I did some reseach and found out about the inspect esmtp setting in the ASA. I have disabled it and i still have to problem. I have also removed all outbound deny statements and still no luck.

Of note is that i can send emails without atachments. They take a long time to go out ( from minutes to hours) but eventually they do. Emails with attachments of even 10k do not go at all.

I was running image 8.2.3 and i downgraded to 8.0.5...still did not work...i upgraded to 8.4.3...still did not work. I am now back at 8.2.3. I would really appreciate some insite into solving this problem.

My Firewall config is atached. I am at my witts end as to what elese to try. The company has not renewed support for the device so i am on my own here! I would really appreciate you help.

Marlon

Users unable to access external email servers ASA even with insp

mirober2 — Wed, 30 Nov 2011 15:08:57 GMT

Hi Marlon,

Do you see any syslogs in ASDM for this traffic when a connection fails? That will give us more information about why this is failing.

-Mike

Users unable to access external email servers ASA even with insp

powermann — Wed, 30 Nov 2011 15:51:00 GMT

Thanks for the response Mirober2

I found a work around for the problem. I looked at the issue from the end point and found that windows 7 handles tcp windowing diffrently than previous OS's. I still think there is an issue somewhere but i am not sure where esle to look so i will work with this for now.

See note below. Thanks for your help guys.

Disable the auto tuning

Check the state or current setting of TCP Auto-Tuning

1. Open elevated command prompt with administrator’s privileges.

2. Type the following command and press Enter:

netsh interface tcp show global

The system will display the following text on screen, where you can check on the Auto-Tuning setting:

Querying active state…

TCP Global Parameters

———————————————-

Receive-Side Scaling State : enabled

Chimney Offload State : enabled

Receive Window Auto-Tuning Level : normal

Add-On Congestion Control Provider : none

ECN Capability : disabled

RFC 1323 Timestamps : disabled

Disable TCP Auto-Tuning

1. Open elevated command prompt with administrator’s privileges.

2. Type the following command and press Enter:

netsh interface tcp set global autotuning=disabled

Enable TCP Auto-Tuning

1. Open elevated command prompt with administrator’s privileges.

2. Type the following command and press Enter:

netsh interface tcp set global autotuning=normal

http://www.mydigitallife.info/disable-tcp-auto-tuning-to-solve-slow-network-cannot-load-web-page-or-download-email-problems-in-vista/