Zimbra via Thunderbird, slow SMTP sending

[feelix]

Hello,
some clients are using Zimbra server via Thunderbird client. With incoming mail there are no issues, but when trying to send mail it takes at least 10-15 seconds till mail is gone. In status dialog box it shows client is connected to Zimbra SMTP server, and it stays like that for mentioned period of time. With Zimbra Web interface everything works flawlessly. Has anyone experienced such an issue, are there any solutions server/client side?

Thanks in advance!

[joho]

We have also noticed this since upgrading from 8.0.9 NE to 8.7.3 NE. This happens every time and does not seem to improve/change with POSTSCREEN learning or not learning.

It also happens when our Helpdesk software send e-mail via Zimbra, using SMTP. So it is definitely not just with Thunderbird.

[phoenix]

This happens every time and does not seem to improve/change with POSTSCREEN learning or not learning.

I'm a bit confused by that statement, Postscreen doesn't actually "learn" anything it's just a (sort of) firewall specifically for postfix - perhaps you're thinking of the ant-spam system in ZCS?

It also happens when our Helpdesk software send e-mail via Zimbra, using SMTP. So it is definitely not just with Thunderbird.

Do you mean that you're submitting mail via port 25 or are you using the correct (authenticated) Submission port 587? Do your log files show anything about the actual delay? I also assume that you don't have and DNS problems? That's one cause of mail delays, have you only noticed this problem after the upgrade or have it been happening for a while? Are you using the DNScache module or other DNS servers?

[geordiejones]

Iv just joined and want to know how to create a new post, can you help, it says in the Q&A bit click new post, but I can't find it, I'm wanting to know if I can make my 4 email addresses come into one mailbox, as I keep having to sign in and out of four different accounts.

Thanks Chris

[joho]

This happens every time and does not seem to improve/change with POSTSCREEN learning or not learning.

I'm a bit confused by that statement, Postscreen doesn't actually "learn" anything it's just a (sort of) firewall specifically for postfix - perhaps you're thinking of the ant-spam system in ZCS?

I was basically quoting Zimbra Support which claimed that this would improve as "Postscreen learned" (sic). So I guess we can strike that one as a possible cause/solution

It also happens when our Helpdesk software send e-mail via Zimbra, using SMTP. So it is definitely not just with Thunderbird.

Do you mean that you're submitting mail via port 25 or are you using the correct (authenticated) Submission port 587? Do your log files show anything about the actual delay? I also assume that you don't have and DNS problems? That's one cause of mail delays, have you only noticed this problem after the upgrade or have it been happening for a while? Are you using the DNScache module or other DNS servers?

We're using the authenticated SMTP/Submission port, and logging in with proper credentials. There are no DNS issues. These problems only surfaced after the upgrade to 8.7.3. We were previously running 8.0.9 and never (!) had these issues

[joho]

This did, indeed, turn out to be a case of DNS issues, created by the installation/upgrade process. We have never had DNS issues before for our Zimbra environment, but that was it. I've written a blog post about it, as well as opened a bug (#107676).

(Blog post is https://www.joho.se/2017/02/28/slow-smt ... ra-server/)