Webmail using HTTP/2
Problem reported by Scarab - 8/20/2020 at 11:22 AM
Pro-Tip: If you are running SmarterMail on Windows Server 2019 and have HTTP/2 enabled in IIS be sure to have at least one IIS binding for SmarterMail that has HTTP/2 disabled!

The SmarterMail webmail screams on HTTP/2. There is definitely a significant performance increase. However, HTTP/2 is *VERY* unforgiving of slow, high latency, noisy, or lossy connections and will result in a spinning loading icon after sign-in. We have experienced a significant number of users who exhibit this problem and each and every one of them was using Wireless 2G, Wireless 802.11 a/b/g, Satellite Internet, 65Kbs ADSL or in one case AOL Dial-Up, and we even had a user with > 60% Packet Loss. Giving them an alternate URI that uses HTTP/1.1 instead resolved their SmarterMail login issues immediately.

In a ideal world HTTP/2 should be preferred, but you may oftentimes have users who have less than ideal connections who still need HTTP/1.1. Always have a backup plan and have at least one IIS binding with HTTP/2 disabled. You'll be glad you do.

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Ron Raley Replied
What non-HTTP/2 binding did you provide to them?

echoDreamz Replied
Weird, we do not have any non HTTP/2 bindings and we have clients from all over the globe on various types of internet from various corners of the world. Never had a complaint about timeouts etc. (unless SM is broken).
Scarab Replied

boonies[dot]mydomain[dot]tld would probably be an apt sub-domain. ;)


We have a lot of webmail users with 15-30GB Inboxes which understandably would have issues loading over slow, lossy, or noisy connections, so it may be a Y.M.M.V. point. However, we've also found it's also been an easy way for us handling customers whose webmail isn't loading due to corrupt browser caches (especially Safari after coming out of Sleep Mode or Hibernation). It's sometimes easier having them try an alternate URI than to find out what browser they have (99% of our users don't know and can't even describe the icon they are clicking on) let alone get them to press something like [CTRL]+[F5] or [SHIFT]+[CMD]+[R] to refresh the cache for webmail, or heaven forbid walking them through their browser's DevTools or Settings.

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