Consequences of a mail server offline?

cron , 3 hours ago

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 OP , 2 hours ago

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

cron , 2 hours ago

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

mozz , 4 hours ago (edited 3 hours ago)

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 OP , 3 hours ago

What if longer? 6 to 8 hours per day?

mozz , 3 hours ago (edited 2 hours ago)

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 OP , 2 hours ago

Thanks for the info. Greatly appreciated.

Max_P , 1 hour ago

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.