I get this, it worked just fine earlier today and have worked for a long time, though if often dies when deleting and in general has quite a lot crashes.
But now it kist dies :-(
(pantheon-mail:9002): GLib-WARNING **: g_set_application_name() called multiple times
[msg] 20:10:10 0.029453 geary-application.vala:205: Mail 1.0.0 prefix=/usr exec_dir=/usr/bin is_installed=true
[deb] 20:10:10 0.039665 null-indicator.vala:13: No messaging menu support in this build
[deb] 20:10:10 0.000846 unity-launcher.vala:44: set unity launcher entry count to 0
[deb] 20:10:10 0.007429 imap-client-session-manager.vala:525: Checking if IMAP host imap.gmail.com/default:993 reachable...
[deb] 20:10:10 0.012649 db-versioned-database.vala:81: VersionedDatabase.upgrade: current database schema for /<email address hidden>/geary.db: 24
[deb] 20:10:10 0.000005 db-versioned-database.vala:62: Looking for schema file: resource:///io/elementary/pantheon-mail/sql/version-024.sql
[deb] 20:10:10 0.000092 db-versioned-database.vala:62: Looking for schema file: resource:///io/elementary/pantheon-mail/sql/version-025.sql
[deb] 20:10:10 0.000558 imap-client-session-manager.vala:525: Checking if IMAP host outlook.office365.com/default:993 reachable...
[deb] 20:10:10 0.012734 db-versioned-database.vala:81: VersionedDatabase.upgrade: current database schema for /<email address hidden>/geary.db: 24
[deb] 20:10:10 0.000004 db-versioned-database.vala:62: Looking for schema file: resource:///io/elementary/pantheon-mail/sql/version-024.sql
[deb] 20:10:10 0.000067 db-versioned-database.vala:62: Looking for schema file: resource:///io/elementary/pantheon-mail/sql/version-025.sql
[deb] 20:10:10 0.000947 imap-db-gc.vala:105: [GC:/<email address hidden>/geary.db] GC state: last_reap_time=2016-08-15T12:57:56+0200 last_vacuum_time=never reaped_messages_since=0 free_page_bytes=327680
[deb] 20:10:10 0.000031 imap-db-gc.vala:128: [GC:/<email address hidden>/geary.db] Reaping last completed on 2016-08-15T12:57:56+0200 (9 days ago)
[deb] 20:10:10 0.000002 imap-db-gc.vala:138: [GC:/<email address hidden>/geary.db] Database never vacuumed (0 messages reaped)
[deb] 20:10:10 0.000091 imap-db-gc.vala:105: [GC:/<email address hidden>/geary.db] GC state: last_reap_time=2016-08-15T12:57:57+0200 last_vacuum_time=never reaped_messages_since=0 free_page_bytes=69632
[deb] 20:10:10 0.000019 imap-db-gc.vala:128: [GC:/<email address hidden>/geary.db] Reaping last completed on 2016-08-15T12:57:57+0200 (9 days ago)
[deb] 20:10:10 0.000002 imap-db-gc.vala:138: [GC:/<email address hidden>/geary.db] Database never vacuumed (0 messages reaped)
[deb] 20:10:10 0.004425 smtp-outbox-folder.vala:139: Starting outbox postman
[deb] 20:10:10 0.001885 smtp-outbox-folder.vala:139: Starting outbox postman
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_get_allocated_height: assertion 'GTK_IS_WIDGET (widget)' failed
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_get_allocated_height: assertion 'GTK_IS_WIDGET (widget)' failed
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_get_allocated_height: assertion 'GTK_IS_WIDGET (widget)' failed
[msg] 20:10:10 0.053314 imap-client-session-manager.vala:536: IMAP host outlook.office365.com/default:993 considered reachable
[msg] 20:10:10 0.000038 imap-client-session-manager.vala:536: IMAP host imap.gmail.com/default:993 considered reachable
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_get_allocated_height: assertion 'GTK_IS_WIDGET (widget)' failed
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_get_allocated_height: assertion 'GTK_IS_WIDGET (widget)' failed
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_get_allocated_height: assertion 'GTK_IS_WIDGET (widget)' failed
[deb] 20:10:10 0.069588 geary-controller.vala:1294: Folder Gmail:<email address hidden>:INBOX (open_count=0 remote_opened=false) selected
[deb] 20:10:10 0.000006 geary-controller.vala:1342: Switching to Gmail:<email address hidden>:INBOX (open_count=0 remote_opened=false)...
(pantheon-mail:9002): Gtk-CRITICAL **: gtk_widget_set_visible: assertion 'GTK_IS_WIDGET (widget)' failed
[deb] 20:10:10 0.008753 imap-engine-minimal-folder.vala:543: Not opening Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true): already open
[deb] 20:10:10 0.000092 imap-engine-minimal-folder.vala:641: Fetching STATUS for remote Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true) from local
[deb] 20:10:10 0.000039 geary-controller.vala:1427: Switched to Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true)
[deb] 20:10:10 0.000217 app-conversation-monitor.vala:309: ConversationMonitor seeding with local email for Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true)
[deb] 20:10:10 0.015596 imap-engine-minimal-folder.vala:645: Fetching information for remote folder Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true)
[deb] 20:10:10 0.000006 imap-account.vala:251: Listing children to find INBOX
[deb] 20:10:10 0.108008 conversation-list-store.vala:427: Adding 44 conversations.
[deb] 20:10:10 0.014593 conversation-list-store.vala:433: Added 44/44 conversations.
[deb] 20:10:10 0.012444 imap-client-session.vala:1455: [0000/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected to imap.gmail.com/default:993
[deb] 20:10:10 0.000005 imap-client-session.vala:624: [0000/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected
[deb] 20:10:10 0.000505 imap-client-session.vala:1455: [0002/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected to imap.gmail.com/default:993
[deb] 20:10:10 0.000003 imap-client-session.vala:624: [0002/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected
[deb] 20:10:10 0.004928 app-conversation-monitor.vala:315: ConversationMonitor seeded for Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true)
[deb] 20:10:10 0.006415 conversation-list-store.vala:211: Loading 44 previews...
[deb] 20:10:10 0.000051 app-email-store.vala:160: EmailStore Gmail:<email address hidden> running GearyAppListOperation on 44 emails
[deb] 20:10:10 0.001923 app-email-store.vala:160: EmailStore Gmail:<email address hidden> running GearyAppListOperation on 1 emails
[deb] 20:10:10 0.001260 geary-controller.vala:2690: Error checking for what operations are supported in the selected conversations: Async transaction cancelled
[deb] 20:10:10 0.000711 imap-client-session.vala:1455: [0001/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected to outlook.office365.com/default:993
[deb] 20:10:10 0.000002 imap-client-session.vala:624: [0001/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected
[deb] 20:10:10 0.001422 app-email-store.vala:182: EmailStore opening Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) for GearyAppListOperation on 1 emails
[deb] 20:10:10 0.002471 imap-engine-minimal-folder.vala:883: Closing replay queue for Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) (flush_pending=true): ReplayQueue:Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) (notification=0 local=0 local_active=true remote=0 remote_active=false)
[deb] 20:10:10 0.000106 imap-engine-replay-queue.vala:452: ReplayQueue.do_replay_local_async ReplayQueue:Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) (notification=0 local=0 local_active=false remote=1 remote_active=false) exiting
[deb] 20:10:10 0.000021 app-email-store.vala:193: EmailStore closed Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) after GearyAppListOperation on 1 emails
[deb] 20:10:10 0.000049 app-email-store.vala:219: EmailStore Gmail:<email address hidden> done running GearyAppListOperation on 1 emails
[deb] 20:10:10 0.028678 imap-engine-replay-queue.vala:561: ReplayQueue.do_replay_remote_async ReplayQueue:Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) (notification=0 local=0 local_active=false remote=0 remote_active=false) exiting
[deb] 20:10:10 0.043585 imap-client-session.vala:1528: [0000/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] capability #1: NAMESPACE IMAP4rev1 X-GM-EXT-1 XYZZY "AUTH=OAUTHBEARER" "AUTH=PLAIN" "AUTH=XOAUTH" "AUTH=PLAIN-CLIENTTOKEN" "AUTH=XOAUTH2" UNSELECT SASL-IR CHILDREN XLIST QUOTA ID IDLE
[deb] 20:10:10 0.000603 imap-engine-minimal-folder.vala:886: Closed replay queue for Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false): ReplayQueue:Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) (notification=0 local=0 local_active=false remote=0 remote_active=false)
[deb] 20:10:10 0.000038 imap-engine-minimal-folder.vala:943: Folder Gmail:<email address hidden>:[Gmail]/All Mail (open_count=0 remote_opened=false) closed
[deb] 20:10:10 0.000520 imap-client-session.vala:718: [0000/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] use_starttls=false is_ssl=true starttls=false
[deb] 20:10:10 0.000005 imap-client-session.vala:746: [0000/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] No STARTTLS attempted
[deb] 20:10:10 0.006631 app-conversation-monitor.vala:700: ConversationMonitor (already opened) reseeding starting from Email ID [4/28828] on opened Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true)
[deb] 20:10:10 0.000318 app-email-store.vala:182: EmailStore opening Gmail:<email address hidden>:INBOX (open_count=2 remote_opened=true) for GearyAppListOperation on 44 emails
[deb] 20:10:10 0.000005 imap-engine-minimal-folder.vala:543: Not opening Gmail:<email address hidden>:INBOX (open_count=3 remote_opened=true): already open
[deb] 20:10:10 0.056460 imap-client-session.vala:1455: [0003/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected to outlook.office365.com/default:993
[deb] 20:10:10 0.000005 imap-client-session.vala:624: [0003/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_CONNECTING] Connected
[deb] 20:10:10 0.005308 imap-client-session.vala:1528: [0002/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] capability #1: NAMESPACE IMAP4rev1 X-GM-EXT-1 XYZZY "AUTH=OAUTHBEARER" "AUTH=PLAIN" "AUTH=XOAUTH" "AUTH=PLAIN-CLIENTTOKEN" "AUTH=XOAUTH2" UNSELECT SASL-IR CHILDREN XLIST QUOTA ID IDLE
[deb] 20:10:10 0.000251 imap-client-session.vala:1528: [0001/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] capability #1: NAMESPACE IMAP4rev1 IMAP4 "AUTH=PLAIN" "AUTH=XOAUTH2" UNSELECT SASL-IR UIDPLUS CHILDREN ID LITERAL+ IDLE
[deb] 20:10:10 0.000566 imap-client-session.vala:718: [0002/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] use_starttls=false is_ssl=true starttls=false
[deb] 20:10:10 0.000006 imap-client-session.vala:746: [0002/imap.gmail.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] No STARTTLS attempted
[deb] 20:10:10 0.000078 imap-client-session.vala:718: [0001/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] use_starttls=false is_ssl=true starttls=false
[deb] 20:10:10 0.000003 imap-client-session.vala:746: [0001/outlook.office365.com/default:993 GEARY_IMAP_CLIENT_SESSION_STATE_NOAUTH] No STARTTLS attempted
[deb] 20:10:10 0.007853 ConversationWidget.vala:213: Failed get URL: Not Found
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'StylishWebView': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'GtkGrid': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'GtkGrid': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'GtkRevealer': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'GtkGrid': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'ConversationWidget': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gtk-WARNING **: drawing failure for widget 'GtkListBox': invalid value (typically too big) for the size of the input (surface, pattern, etc.)
(pantheon-mail:9002): Gdk-ERROR **: The program 'pantheon-mail' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadAlloc (insufficient resources for operation)'.
(Details: serial 5032 error_code 11 request_code 53 (core protocol) minor_code 0)
(Note to programmers: normally, X errors are reported asynchronously;
that is, you will receive the error a while after causing it.
To debug your program, run it with the GDK_SYNCHRONIZE environment
variable to change this behavior. You can then get a meaningful
backtrace from your debugger if you break on the gdk_x_error() function.)
Trace/breakpoint trap (core dumped)
This also affects me, however, it only happens when trying to open an email with many replies (I think thirty is the right number to crash it, although it may just be a size thing rather than a number of replies thing). What must be happening here is that you've got "Automatically select next message" selected, and your most recent email in your main inbox happens to have many replies. I have no idea how to fix this, though.