I could reproduce the issue every single time in the following way after resetting:
(Resolution:1366X768, dock will be always visible)
Version: elementary OS 0.4 Loki
Mail Version: Mail 1.0.2
System is up-to-date when I'm writing this.
Step 1: Reset mail with dconf reset -f /org/pantheon/mail/
Step 2: Open mail and here is the dump
messages-pane-position=416
folder-list-pane-position-horizontal=149
window-width=1059
Step 3: Maximize mail
window-maximize=true
messages-pane-position=631
folder-list-pane-position-horizontal=149
window-height=690
window-width=1366
Step 4: Decrease the size of message pane position(In other words, increase the second section width by the slider present)more than the size of the resolution
window-maximize=true
messages-pane-position=1078
folder-list-pane-position-horizontal=149
window-height=690
window-width=1571
Now if you notice the width increased more than the resolution.
Step 5: Restore mail
window-maximize=false
messages-pane-position=1065
folder-list-pane-position-horizontal=149
window-height=610
window-width=1707
Step 6: Close and open mail again
Ever increasing!
window-maximize=false
messages-pane-position=1136
folder-list-pane-position-horizontal=149
window-height=610
window-width=1806
(Sometimes, you don't need to do this step, after the step 5, it's ever-increasing)
I could reproduce the issue every single time in the following way after resetting: 1366X768, dock will be always visible)
(Resolution:
Version: elementary OS 0.4 Loki
Mail Version: Mail 1.0.2
System is up-to-date when I'm writing this.
Step 1: Reset mail with dconf reset -f /org/pantheon/mail/
Step 2: Open mail and here is the dump pane-position= 416 list-pane- position- horizontal= 149
messages-
folder-
window-width=1059
Step 3: Maximize mail maximize= true pane-position= 631 list-pane- position- horizontal= 149
window-
messages-
folder-
window-height=690
window-width=1366
Step 4: Decrease the size of message pane position(In other words, increase the second section width by the slider present)more than the size of the resolution maximize= true pane-position= 1078 list-pane- position- horizontal= 149
window-
messages-
folder-
window-height=690
window-width=1571
Now if you notice the width increased more than the resolution.
Step 5: Restore mail maximize= false pane-position= 1065 list-pane- position- horizontal= 149
window-
messages-
folder-
window-height=610
window-width=1707
Step 6: Close and open mail again maximize= false pane-position= 1136 list-pane- position- horizontal= 149
Ever increasing!
window-
messages-
folder-
window-height=610
window-width=1806
(Sometimes, you don't need to do this step, after the step 5, it's ever-increasing)