this post was submitted on 18 Jul 2024
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Consequences of a mail server offline? (lemmy.ml)
submitted 4 months ago* (last edited 4 months ago) by umami_wasbi@lemmy.ml to c/selfhosted@lemmy.world
22 comments fedilink hide all child comments
 

Just wonder what if my mail server went offline for some periods, and the sending party couldn't deliver.

Will there be any consequences except I don't get the mail? I tried searching but they all in the perspective of a sender and get a bounce, rather the other way around.

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[–] mozz@mbin.grits.dev 33 points 4 months ago* (last edited 4 months ago) (1 children)

SMTP is designed with queues and retries

Unless something has changed massively since I was deeply involved with this stuff, the people that sent you email may get a notification after some hours that their message is being delayed, and maybe after like 24-48 hours they might get a bounce. But if it’s just your SMTP server going down for an hour or two every now and then, the system should be able handle that seamlessly (barring some hiccups like messages showing up with timestamps hours in the past which sometimes is confusing).

[–] umami_wasbi@lemmy.ml 5 points 4 months ago (2 children)

What if longer? 6 to 8 hours per day?

[–] Max_P@lemmy.max-p.me 15 points 4 months ago (1 children)

The problem with this is the probability of your server being available for the next retry is fairly low.

Usually some sort of exponential backoff is used so it might retry after 5 minutes, 15 minutes, an hour, 3 hours, 6 hours, 24 hours, 48 hours, give up.

6-8 hours is probably too much for anything serious where you don't want emails to just drop. It will work so if you're just using it to sign up to sites and stuff, you can make sure your server is on to receive the verification emails and stuff. But I wouldn't use it for anything important.

[–] umami_wasbi@lemmy.ml 1 points 4 months ago

Oh yeah. I didn't think of that. Thanks for the heads up.

[–] mozz@mbin.grits.dev 5 points 4 months ago* (last edited 4 months ago) (1 children)

I think 8 hours starts to get into territory where they might get an informational message about the delay? That also starts to be long enough that the emails might get lost in the distant past in the client and never be seen, by the time they arrive.

I think when I used to do this, it was one advisory message every 24 hours that a message was holding in the queue, and after 5 days it would bounce, but I have to assume that those limits have shrunk in the modern day. How much, IDK; it might be worth experimenting with it though before committing to creating that situation since it might not go okay.

[–] umami_wasbi@lemmy.ml 3 points 4 months ago

Thanks for the info. Greatly appreciated.

[–] cron@feddit.org 15 points 4 months ago (1 children)

Some things to consider:

  • It is typical for mail servers to retry a couple of times for maybe a day or two. The exact values can differ a lot.
  • After this time, the message bounces and the sender (sometimes) gets notified.
  • This bounce might get your address removed from newsletters.
[–] umami_wasbi@lemmy.ml 3 points 4 months ago (1 children)

So noting substantial other than I don't get the mail and might get kick out of newsletters?

[–] cron@feddit.org 9 points 4 months ago (1 children)

Correct. But at least for me, even the low risk of some e-mails getting lost is pretty substantial.

[–] ErwinLottemann@feddit.de 1 points 4 months ago (1 children)

if you need more reliability you can always use a second mailserver as backup, add a second mx record to your domain and if the first one is not responding the second one will be used. there is no limit of how many next servers there can be specified afaik.

[–] cron@feddit.org 3 points 4 months ago (1 children)

Sure. But you could also just not turn off the mail server for a start ;)

[–] umami_wasbi@lemmy.ml 1 points 3 months ago (1 children)

True, but I had the crazy idea of running it on my laptop that goes with me.

[–] cron@feddit.org 1 points 3 months ago (1 children)

That's a truely unusual way. Why not set it up on a raspberry pi?

[–] umami_wasbi@lemmy.ml 1 points 3 months ago* (last edited 3 months ago)

In the name of science? And a laptop is what I only have rn.

[–] ikidd@lemmy.world 4 points 4 months ago (1 children)

If you're concerned about missing emails, you might want to sign up for a forwarder instead. I don't see the point of running an email server that's going to be off for long periods of time.

Generally it's not going to put you on a blacklist if a sending server doesn't manage to send, but some have very short queue times before they'll drop it, so you're going to miss a lot of mail that way.

[–] umami_wasbi@lemmy.ml 1 points 4 months ago* (last edited 4 months ago)

Having control while not having my PC up the whole day?