SMTP email stopped working 10 days ago (curl works; server doesn't have SMTPS)

Installation
1

Hi All,

I’ve had my site running for a few years without issue now. All of a sudden, SMTP simply stopped working. (I made no config changes on host or in the container).

I’m using SMTP (not SMTPS). I entered the discourse container and tested that I could send mails using curl:

curl smtp://mail.example.com --mail-from myself@example.com --mail-rcpt receiver@example.com --upload-file email.txt

However Discourse doesn’t send any email and the logs simply say

Net::ReadTimeout with #<Socket:(closed)>

Postfix logs on the host say:

connect from unknown[172.17.0.5]
lost connection after CONNECT from unknown[172.17.0.5]
disconnect from unknown[172.17.0.5] commands=0/0

Does anyone have any idea what could have changed?

Thanks in advance.

GI

PS: Sorry the first version of this post got truncated by accident and only half the message posted. I just edited it.

2

Hi All,

I chased the problem down. Turns out the host is now imposing a 7 second delay on all incoming mail (even from containers). Discourse times out by default in 5 seconds.
I increased it to 10 seconds in containers/app.yml:

DISCOURSE_SMTP_OPEN_TIMEOUT: 10
DISCOURSE_SMTP_READ_TIMEOUT: 10

It works now… but does anyone know how to get rid of the postfix delay on the host? I’ve been searching through the config files but cant find anything…

GI

3

If you’re using postscreen, see postscreen_greet_wait and postscreen_greet_action.

If not, this may be due to DNS timing out on a reverse lookup of the connecting IP.

2 Likes
4

Ha! Thank you so much! This was exactly the problem.

I just added static IP addresses (with dummy host names) for all IP addresses docker will typically assign (172.17.0.2 through 10). So if my container comes up with a different IP, hopefully it won’t stall on the nslookup.

I wonder if there’s a way for docker to resolve IP addresses of alll containers…

Thanks again

1 Like
5

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