Adding two accounts on slow internet connection makes Mail freeze and crash

## What Happened
I installed eOS 6 freshly today and configured it to my needs. I am currently on a very slow internet connection (when it's good it's about 200 kb/s, but I've also observed 10kb/s). Having a single IMAP account in online accounts works nicely, I could see the mail of both accounts individually. But when I add them in any order and open Mail, it freezes and after a while I get an dialog asking me whether to wait or force quit Mail. It was showing only the "All Mailboxes" part and I could switch between "Inbox", "Archive" and "Sent", but the message list and message preview panels stayed empty. I also could not close the window, clicking the "X" did nothing.

I've tried this a few times and it always froze and crashed. But just now it worked and now it shows both accounts as desired. And now I've restarted Mail and it freezes and again. So my guess is that due to my bad internet connection, fetching the emails runs into a timeout which leads to a crash.

## Expected Behavior

Multiple online accounts should show up in Mail. Additionally, Mail should show loading indicators while it is loading.

## Steps to Reproduce

(Difficult to test whether this is a reliable reproduction.)

1. Use a slow internet connection.
2. Add two online IMAP accounts.
3. Open Mail.
4. Watch it freeze and crash.

### Logs

During this log I clicked on the "Inbox", "Archive" and "Sent" folders and then tried to close the window by clicking on the "X".

```
(process:3758): GLib-GIO-DEBUG: 22:48:49.574: _g_io_module_get_default: Found default implementation dconf (DConfSettingsBackend) for ?gsettings-backend?
(process:3758): dconf-DEBUG: 22:48:49.574: watch_fast: "/io/elementary/mail/" (establishing: 0, active: 0)
(process:3758): GLib-DEBUG: 22:48:49.574: unsetenv() is not thread-safe and should not be used after threads are created
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.578: watch_established: "/io/elementary/mail/" (establishing: 1)
(io.elementary.mail:3758): GLib-GIO-DEBUG: 22:48:49.601: _g_io_module_get_default: Found default implementation gvfs (GDaemonVfs) for ‘gio-vfs’
(io.elementary.mail:3758): GLib-DEBUG: 22:48:49.646: unsetenv() is not thread-safe and should not be used after threads are created
(io.elementary.mail:3758): Gtk-DEBUG: 22:48:49.646: Connecting to session manager
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.699: watch_fast: "/io/elementary/mail/" (establishing: 0, active: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.700: watch_fast: "/io/elementary/mail/" (establishing: 0, active: 2)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.705: watch_fast: "/org/gnome/evolution-data-server/" (establishing: 0, active: 0)
(io.elementary.mail:3758): GLib-GIO-DEBUG: 22:48:49.705: Failed to initialize portal (GNetworkMonitorPortal) for gio-network-monitor: Not using portals
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.706: watch_established: "/org/gnome/evolution-data-server/" (establishing: 1)
(io.elementary.mail:3758): GLib-GIO-DEBUG: 22:48:49.709: _g_io_module_get_default: Found default implementation networkmanager (GNetworkMonitorNM) for ‘gio-network-monitor’
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.709: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.709: change_notify: /org/gnome/evolution-data-server/network-monitor-gio-name
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.719: watch_fast: "/io/elementary/mail/" (establishing: 0, active: 3)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.719: watch_fast: "/org/gnome/evolution/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:49.720: watch_established: "/org/gnome/evolution/" (establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_fast: "/system/proxy/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_fast: "/system/proxy/http/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_fast: "/system/proxy/https/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_established: "/system/proxy/" (establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_fast: "/system/proxy/ftp/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_fast: "/system/proxy/socks/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: unwatch_fast: "/system/proxy/" (active: 1, establishing: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: watch_established: "/system/proxy/http/" (establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.028: unwatch_fast: "/system/proxy/http/" (active: 1, establishing: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.029: watch_established: "/system/proxy/https/" (establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.029: unwatch_fast: "/system/proxy/https/" (active: 1, establishing: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.029: unwatch_fast: "/system/proxy/ftp/" (active: 0, establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.029: unwatch_fast: "/system/proxy/socks/" (active: 0, establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.030: watch_established: "/system/proxy/ftp/" (establishing: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.030: watch_established: "/system/proxy/socks/" (establishing: 0)
(io.elementary.mail:3758): GLib-GIO-DEBUG: 22:48:50.052: _g_io_module_get_default: Found default implementation libproxy (GLibproxyResolver) for ‘gio-proxy-resolver’
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.062: watch_fast: "/io/elementary/mail/accounts/e715d8863086995caabbbddd0427151051e6aac5/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.062: watch_established: "/io/elementary/mail/accounts/e715d8863086995caabbbddd0427151051e6aac5/" (establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.062: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.064: change_notify: /io/elementary/mail/accounts/e715d8863086995caabbbddd0427151051e6aac5/expanded
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.075: watch_fast: "/io/elementary/mail/accounts/c9ec98fc2eef3200c4aa4e1806637ea9b9b22c01/" (establishing: 0, active: 0)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.076: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.076: change_notify: /io/elementary/mail/accounts/c9ec98fc2eef3200c4aa4e1806637ea9b9b22c01/expanded
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.077: watch_established: "/io/elementary/mail/accounts/c9ec98fc2eef3200c4aa4e1806637ea9b9b22c01/" (establishing: 1)
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.327: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:48:50.330: change_notify: /io/elementary/mail/window-maximized
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.791: CLIENT[0x560ddc1daa10]: Starting synchronous TLS handshake
(io.elementary.mail:3758): GLib-GIO-DEBUG: 22:48:50.791: _g_io_module_get_default: Found default implementation gnutls (GTlsBackendGnutls) for ‘gio-tls-backend’
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.791: CLIENT[0x560ddc1db250]: Starting synchronous TLS handshake
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.810: CLIENT[0x560ddc1daa10]: TLS handshake thread starts
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.810: CLIENT[0x560ddc1daa10]: claiming operation OP_HANDSHAKE
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.810: CLIENT[0x560ddc1daa10]: claiming operation OP_HANDSHAKE succeeded
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.914: CLIENT[0x560ddc1db250]: TLS handshake thread starts
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.914: CLIENT[0x560ddc1db250]: claiming operation OP_HANDSHAKE
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:50.914: CLIENT[0x560ddc1db250]: claiming operation OP_HANDSHAKE succeeded
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.105: CLIENT[0x560ddc1daa10]: verifying peer certificate
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.131: CLIENT[0x560ddc1db250]: verifying peer certificate
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1daa10]: TLS handshake thread succeeded
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1db250]: TLS handshake thread succeeded
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1daa10]: synchronous TLS handshake thread completed
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1daa10]: finishing TLS handshake
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1daa10]: TLS handshake has finished successfully
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1db250]: synchronous TLS handshake thread completed
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.145: CLIENT[0x560ddc1db250]: finishing TLS handshake
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1db250]: TLS handshake has finished successfully
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1db250]: yielding operation OP_HANDSHAKE
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1db250]: starting to read data from TLS connection
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1db250]: claiming operation OP_READ
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1db250]: claiming operation OP_READ succeeded
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1daa10]: yielding operation OP_HANDSHAKE
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1daa10]: starting to read data from TLS connection
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1daa10]: claiming operation OP_READ
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.146: CLIENT[0x560ddc1daa10]: claiming operation OP_READ succeeded
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.242: CLIENT[0x560ddc1daa10]: yielding operation OP_READ
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.242: CLIENT[0x560ddc1daa10]: successfully read 260 bytes from TLS connection
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.243: CLIENT[0x560ddc1db250]: yielding operation OP_READ
(io.elementary.mail:3758): GLib-Net-DEBUG: 22:48:51.243: CLIENT[0x560ddc1db250]: successfully read 260 bytes from TLS connection

(io.elementary.mail:3758): camel-CRITICAL **: 22:48:51.243: MailBackendSimpleSasl has an empty CamelServiceAuthType
(io.elementary.mail:3758): dconf-DEBUG: 22:48:54.660: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:48:54.661: change_notify: /io/elementary/mail/selected-folder
(io.elementary.mail:3758): dconf-DEBUG: 22:49:56.688: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:49:56.692: change_notify: /io/elementary/mail/selected-folder
(io.elementary.mail:3758): dconf-DEBUG: 22:49:56.809: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:49:56.809: change_notify: /io/elementary/mail/window-maximized
(io.elementary.mail:3758): dconf-DEBUG: 22:49:57.921: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:49:57.922: change_notify: /io/elementary/mail/selected-folder
(io.elementary.mail:3758): dconf-DEBUG: 22:49:58.820: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:49:58.821: change_notify: /io/elementary/mail/selected-folder
(io.elementary.mail:3758): dconf-DEBUG: 22:50:05.881: change_fast
(io.elementary.mail:3758): dconf-DEBUG: 22:50:05.882: change_notify: /io/elementary/mail/window-maximized

(io.elementary.mail:3758): GLib-GObject-WARNING **: 22:50:07.091: ../../../gobject/gsignal.c:2736: instance '0x560ddc4ab1e0' has no handler with id '215'
(io.elementary.mail:3758): dconf-DEBUG: 22:50:07.091: unwatch_fast: "/io/elementary/mail/" (active: 4, establishing: 0)

```

## Platform Information

elemantary OS 6
Mail 6.1.0