[Bug 1799345] [NEW] Sypheed not (or no longer) using SNI for SSL connections

[Launchpad Bug Tracker]

You have been subscribed to a public bug by vofka (vofka):

IMAP connection to imap.gmail.com over SSL returns self-signed
certificate. Though you can still connect to imap.gmail.com using this
certificate, it would be better to fix it to avoid this scary warning
(self-signed certificate) and provide a smoother user experience.

Test Case
Create IMAP account for gmail.com in sylpheed. To do this, select "Create new account" from the "Configuration" in the main menu. "New account setup" window will appear. Select "IMAP4 (Gmail)" and follow instructions in that window. After setup is finished check for new email for newly created account. You should get a warning complaining about self-signed certificate.
With fixed package, try the same. This time you should not get the warning.

Original Description
--------------------
Problem appeared after upgrading from Ubuntu 18.04 to 18.10.
When starting Sylpheed, connecting to imap.gmail.com over SSL, I get a warning embedded in the SSL certificate:  "Subject: /OU=No SNI provided; please fix your client./CN=invalid2.invalid "

May be related to this bug report about 'fetchmail' in redhat enterprise when it was still using TLSv1.2 instead of TLSv1.3:
https://bugzilla.redhat.com/show_bug.cgi?id=1611815
https://gitlab.com/fetchmail/fetchmail/commit/9b8b634312f169fab872f3580c2febe5af031615

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: sylpheed 3.5.1-1ubuntu3
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
CurrentDesktop: XFCE
Date: Tue Oct 23 00:27:01 2018
InstallationDate: Installed on 2016-06-05 (869 days ago)
InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: sylpheed
UpgradeStatus: Upgraded to cosmic on 2018-10-21 (1 days ago)
modified.conffile..etc.default.apport: [modified]
mtime.conffile..etc.default.apport: 2018-03-20T22:16:27.108498

** Affects: sylpheed (Ubuntu)
     Importance: Undecided
         Status: Triaged


** Tags: amd64 apport-bug bionic cosmic patch
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Sypheed not (or no longer) using SNI for SSL connections
https://bugs.launchpad.net/bugs/1799345
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