<s>
Mozilla	B-Application
Thunderbird	I-Application
is	O
a	O
free	B-License
and	I-License
open-source	I-License
cross-platform	B-Operating_System
email	B-Protocol
client	I-Protocol
,	O
personal	B-Application
information	I-Application
manager	I-Application
,	O
news	B-Protocol
client	I-Protocol
,	O
RSS	O
and	O
chat	O
client	O
that	O
is	O
operated	O
by	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
's	O
subsidiary	O
MZLA	O
Technologies	O
Corporation	O
.	O
</s>
<s>
Thunderbird	B-Application
is	O
an	O
independent	O
,	O
community-driven	O
project	O
that	O
is	O
managed	O
and	O
overseen	O
by	O
the	O
Thunderbird	B-Application
Council	O
,	O
which	O
is	O
elected	O
by	O
the	O
Thunderbird	B-Application
Community	O
.	O
</s>
<s>
The	O
project	O
strategy	O
was	O
originally	O
modeled	O
after	O
that	O
of	O
Mozilla	B-Application
's	I-Application
Firefox	I-Application
web	B-Application
browser	I-Application
and	O
is	O
an	O
interface	O
built	O
on	O
top	O
of	O
that	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
Thunderbird	B-Application
is	O
an	O
email	O
,	O
newsgroup	O
,	O
news	O
feed	O
,	O
and	O
chat	O
(	O
XMPP/IRC	O
)	O
client	O
with	O
personal	B-Application
information	I-Application
manager	I-Application
(	O
PIM	O
)	O
functionality	O
,	O
inbuilt	O
since	O
version	O
78.0	O
and	O
previously	O
available	O
from	O
the	O
Lightning	B-Language
calendar	B-Application
extension	O
.	O
</s>
<s>
Additional	O
features	O
are	O
available	O
from	O
extensions	B-Operating_System
.	O
</s>
<s>
Thunderbird	B-Application
manages	O
multiple	O
email	O
,	O
newsgroup	O
,	O
and	O
news	O
feed	O
accounts	O
and	O
supports	O
multiple	O
identities	O
within	O
accounts	O
.	O
</s>
<s>
Features	O
such	O
as	O
quick	O
search	O
,	O
saved	O
search	O
folders	O
(	O
"	O
virtual	O
folders	O
"	O
)	O
,	O
advanced	O
message	O
filtering	B-Application
,	O
message	O
grouping	O
,	O
and	O
tags	O
help	O
manage	O
and	O
find	O
messages	O
.	O
</s>
<s>
On	O
Linux-based	O
systems	O
,	O
system	O
mail	O
(	O
movemail	B-Protocol
)	O
accounts	O
were	O
supported	O
until	O
version	O
91.0	O
.	O
</s>
<s>
Thunderbird	B-Application
provides	O
basic	O
support	O
for	O
system-specific	O
new	O
email	O
notifications	O
and	O
can	O
be	O
extended	O
with	O
advanced	O
notification	O
support	O
using	O
an	O
add-on	B-Operating_System
.	O
</s>
<s>
Thunderbird	B-Application
incorporates	O
a	O
Bayesian	B-Application
spam	I-Application
filter	I-Application
,	O
a	O
whitelist	O
based	O
on	O
the	O
included	O
address	O
book	O
,	O
and	O
can	O
also	O
understand	O
classifications	O
by	O
server-based	O
filters	O
such	O
as	O
SpamAssassin	B-Language
.	O
</s>
<s>
Extensions	B-Operating_System
allow	O
the	O
addition	O
of	O
features	O
through	O
the	O
installation	O
of	O
XPInstall	B-Application
modules	O
(	O
known	O
as	O
"	O
XPI	B-Application
"	O
or	O
"	O
zippy	O
"	O
installation	O
)	O
via	O
the	O
add-ons	B-Operating_System
website	O
that	O
also	O
features	O
an	O
update	O
functionality	O
to	O
update	O
the	O
extensions	B-Operating_System
.	O
</s>
<s>
Thunderbird	B-Application
supports	O
a	O
variety	O
of	O
themes	B-Application
for	O
changing	O
its	O
overall	O
look	O
and	O
feel	O
.	O
</s>
<s>
These	O
packages	O
of	O
CSS	B-Language
and	O
image	B-Algorithm
files	O
can	O
be	O
downloaded	O
via	O
the	O
add-ons	B-Operating_System
website	O
at	O
Mozilla	O
Add-ons	B-Operating_System
.	O
</s>
<s>
Thunderbird	B-Application
follows	O
industry	O
standards	O
for	O
email	O
:	O
</s>
<s>
POP	B-Protocol
.	O
</s>
<s>
IMAP	B-Protocol
.	O
</s>
<s>
Thunderbird	B-Application
has	O
implemented	O
many	O
of	O
the	O
capabilities	O
in	O
IMAP	B-Protocol
,	O
in	O
addition	O
to	O
adding	O
their	O
own	O
extensions	B-Operating_System
and	O
the	O
de	O
facto	O
standards	O
by	O
Google	O
and	O
Apple	O
.	O
</s>
<s>
LDAP	B-Protocol
address	O
auto-completion	O
.	O
</s>
<s>
S/MIME	B-Protocol
:	O
Inbuilt	O
support	O
for	O
email	O
encryption	O
and	O
signing	O
using	O
X.509	O
keys	O
provided	O
by	O
a	O
centralised	O
certificate	O
authority	O
.	O
</s>
<s>
OpenPGP	O
:	O
Inbuilt	O
support	O
for	O
email	O
encryption	O
and	O
signing	O
since	O
version	O
78.2.1	O
,	O
while	O
older	O
versions	O
used	O
extensions	B-Operating_System
such	O
as	O
Enigmail	B-Operating_System
.	O
</s>
<s>
news	B-Application
aggregators	I-Application
)	O
,	O
it	O
supports	O
Atom	B-Application
and	O
RSS	O
.	O
</s>
<s>
For	O
chat	O
,	O
it	O
supports	O
the	O
IRC	B-Protocol
and	O
XMPP	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
For	O
newsfeeds	B-Application
,	O
it	O
uses	O
NNTP	B-Protocol
and	O
supports	O
NNTPS	B-Protocol
.	O
</s>
<s>
Thunderbird	B-Application
provides	O
mailbox	O
format	O
support	O
using	O
plugins	B-Application
,	O
but	O
this	O
feature	O
is	O
not	O
yet	O
enabled	O
due	O
to	O
related	O
work	O
in	O
progress	O
.	O
</s>
<s>
Thunderbird	B-Application
also	O
uses	O
Mork	B-Application
and	O
(	O
since	O
version	O
3	O
)	O
MozStorage	O
(	O
which	O
is	O
based	O
on	O
SQLite	B-Language
)	O
for	O
its	O
internal	O
database	O
.	O
</s>
<s>
Mork	B-Application
was	O
due	O
to	O
be	O
replaced	O
with	O
MozStorage	O
in	O
Thunderbird	B-Application
3.0	O
,	O
but	O
the	O
8.0	O
release	O
still	O
uses	O
the	O
Mork	B-Application
file	O
format	O
.	O
</s>
<s>
Since	O
version	O
38	O
,	O
Thunderbird	B-Application
has	O
integrated	O
support	O
for	O
automatic	O
linking	O
of	O
large	O
files	O
instead	O
of	O
attaching	O
them	O
directly	O
to	O
the	O
mail	O
message	O
.	O
</s>
<s>
Thunderbird	B-Application
provides	O
a	O
wysiwyg	B-Application
editor	I-Application
for	O
composing	O
messages	O
formatted	O
with	O
HTML	B-Language
(	O
default	O
)	O
.	O
</s>
<s>
The	O
Insert	O
>	O
HTML	B-Language
menu	O
provides	O
the	O
ability	O
to	O
edit	O
the	O
HTML	B-Language
source	O
code	O
of	O
the	O
message	O
.	O
</s>
<s>
There	O
is	O
basic	O
support	O
for	O
HTML	B-Language
template	O
messages	O
,	O
which	O
are	O
stored	O
in	O
a	O
dedicated	O
templates	O
folder	O
for	O
each	O
account	O
.	O
</s>
<s>
Markdown	O
support	O
is	O
provided	O
through	O
the	O
add-on	B-Operating_System
.	O
</s>
<s>
For	O
example	O
,	O
POP3	B-Protocol
folders	O
are	O
subject	O
to	O
filesystem	O
design	O
limitations	O
,	O
such	O
as	O
maximum	O
file	O
sizes	O
on	O
filesystems	O
that	O
do	O
not	O
have	O
large-file	B-Application
support	I-Application
,	O
as	O
well	O
as	O
possible	O
limitations	O
of	O
long	O
filenames	O
,	O
and	O
other	O
issues	O
.	O
</s>
<s>
Thunderbird	B-Application
runs	O
on	O
a	O
variety	O
of	O
platforms	O
.	O
</s>
<s>
Ports	O
for	O
older	O
versions	O
available	O
for	O
OS/2	B-Application
(	O
including	O
ArcaOS	B-Device
and	O
eComStation	B-Device
)	O
.	O
</s>
<s>
In	O
June	O
2022	O
,	O
the	O
Thunderbird	B-Application
project	O
announced	O
that	O
it	O
would	O
be	O
collaborating	O
with	O
email	B-Protocol
client	I-Protocol
K-9	B-Application
for	O
Android	B-Application
to	O
build	O
a	O
Thunderbird	B-Application
version	O
for	O
Android	B-Application
.	O
</s>
<s>
To	O
this	O
end	O
,	O
K-9	B-Application
lead	O
developer	O
Christian	O
Ketterer	O
joined	O
the	O
Thunderbird	B-Application
team	O
in	O
2022	O
.	O
</s>
<s>
The	O
plan	O
was	O
to	O
transform	O
K-9	B-Application
Mail	I-Application
into	O
Thunderbird	B-Application
on	O
Android	B-Application
,	O
including	O
the	O
respective	O
name	O
change	O
and	O
adoption	O
of	O
the	O
Thunderbird	B-Application
branding	O
.	O
</s>
<s>
As	O
soon	O
as	O
K-9	B-Application
Mail	I-Application
had	O
been	O
brought	O
into	O
alignment	O
with	O
Thunderbird	B-Application
's	O
feature	O
set	O
and	O
visual	O
appearance	O
,	O
this	O
changeover	O
would	O
take	O
place	O
,	O
according	O
to	O
Thunderbird	B-Application
's	O
Jason	O
Evangelho	O
.	O
</s>
<s>
With	O
contributors	O
all	O
over	O
the	O
world	O
,	O
Thunderbird	B-Application
has	O
been	O
translated	O
into	O
more	O
than	O
65	O
languages	O
,	O
although	O
email	O
addresses	O
are	O
currently	O
limited	O
to	O
ASCII	O
local	O
parts	O
.	O
</s>
<s>
Thunderbird	B-Application
does	O
not	O
yet	O
support	O
SMTPUTF8	O
(	O
RFC	O
6531	O
)	O
or	O
Email	O
Address	O
Internationalization	O
.	O
</s>
<s>
Thunderbird	B-Application
provides	O
security	O
features	O
such	O
as	O
TLS/SSL	B-Protocol
connections	O
to	O
IMAP	B-Protocol
and	O
SMTP	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
It	O
also	O
offers	O
inbuilt	O
support	O
for	O
secure	O
email	O
with	O
digital	O
signing	O
and	O
message	O
encryption	O
through	O
OpenPGP	O
(	O
using	O
public	O
and	O
private	O
keys	O
)	O
or	O
S/MIME	B-Protocol
(	O
using	O
certificates	O
)	O
.	O
</s>
<s>
Any	O
of	O
these	O
security	O
features	O
can	O
take	O
advantage	O
of	O
smartcards	O
with	O
the	O
installation	O
of	O
additional	O
extensions	B-Operating_System
.	O
</s>
<s>
Other	O
security	O
features	O
may	O
be	O
added	O
through	O
extensions	B-Operating_System
.	O
</s>
<s>
Up	O
to	O
version	O
68	O
,	O
the	O
Enigmail	B-Operating_System
extension	O
was	O
required	O
for	O
OpenPGP	O
support	O
(	O
now	O
inbuilt	O
)	O
.	O
</s>
<s>
Optional	O
security	O
protections	O
also	O
include	O
disabling	O
loading	O
of	O
remote	O
images	O
within	O
messages	O
,	O
enabling	O
only	O
specific	O
media	O
types	O
(	O
sanitizer	O
)	O
,	O
and	O
disabling	O
JavaScript	B-Language
.	O
</s>
<s>
The	O
French	O
military	O
uses	O
Thunderbird	B-Application
and	O
contributes	O
to	O
its	O
security	O
features	O
,	O
which	O
are	O
claimed	O
to	O
match	O
the	O
requirements	O
for	O
NATO	O
's	O
closed	O
messaging	O
system	O
.	O
</s>
<s>
Originally	O
launched	O
as	O
Minotaur	O
shortly	O
after	O
Phoenix	B-Application
(	O
the	O
original	O
name	O
for	O
Mozilla	B-Application
Firefox	I-Application
)	O
,	O
the	O
project	O
failed	O
to	O
gain	O
momentum	O
.	O
</s>
<s>
With	O
the	O
success	O
of	O
Firefox	B-Application
,	O
however	O
,	O
demand	O
increased	O
for	O
a	O
mail	B-Protocol
client	I-Protocol
to	O
go	O
with	O
it	O
,	O
and	O
the	O
work	O
on	O
Minotaur	O
was	O
revived	O
under	O
the	O
new	O
name	O
of	O
Thunderbird	B-Application
,	O
and	O
migrated	O
to	O
the	O
new	O
toolkit	O
developed	O
by	O
the	O
Firefox	B-Application
team	O
.	O
</s>
<s>
Significant	O
work	O
on	O
Thunderbird	B-Application
restarted	O
with	O
the	O
announcement	O
that	O
from	O
version	O
1.5	O
onward	O
the	O
main	O
Mozilla	O
suite	O
would	O
be	O
designed	O
around	O
separate	O
applications	O
using	O
this	O
new	O
toolkit	O
.	O
</s>
<s>
The	O
original	O
Mozilla	O
Suite	O
continues	O
to	O
be	O
developed	O
as	O
SeaMonkey	B-Language
.	O
</s>
<s>
On	O
December	O
23	O
,	O
2004	O
,	O
Project	B-Language
Lightning	I-Language
was	O
announced	O
which	O
tightly	O
integrated	O
calendar	B-Application
functionality	O
(	O
scheduling	O
,	O
tasks	O
,	O
etc	O
.	O
)	O
</s>
<s>
into	O
Thunderbird	B-Application
.	O
</s>
<s>
Lightning	B-Language
supports	O
the	O
full	O
range	O
of	O
calendar	B-Application
mechanisms	O
and	O
protocols	O
supported	O
by	O
the	O
Mozilla	O
Calendar	B-Application
infrastructure	O
,	O
just	O
as	O
with	O
modern	O
(	O
post-0.2	O
)	O
Sunbird	O
.	O
</s>
<s>
On	O
October	O
11	O
,	O
2006	O
,	O
Qualcomm	O
and	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
announced	O
that	O
"	O
future	O
versions	O
of	O
Eudora	B-Operating_System
will	O
be	O
based	O
upon	O
the	O
same	O
technology	O
platform	O
as	O
the	O
open	O
source	O
Mozilla	B-Application
Thunderbird	I-Application
email	O
program.	O
"	O
</s>
<s>
The	O
project	O
was	O
code-named	O
Penelope	B-Protocol
.	O
</s>
<s>
In	O
late	O
2006	O
,	O
Debian	O
rebranded	O
Thunderbird	B-Application
as	O
Icedove	B-Operating_System
due	O
to	O
trademark	O
and	O
copyright	O
reasons	O
.	O
</s>
<s>
On	O
July	O
26	O
,	O
2007	O
,	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
announced	O
that	O
Thunderbird	B-Application
would	O
be	O
developed	O
by	O
an	O
independent	O
organization	O
,	O
because	O
the	O
Mozilla	O
Corporation	O
(	O
a	O
subsidiary	O
of	O
the	O
foundation	O
)	O
was	O
focusing	O
on	O
Mozilla	B-Application
Firefox	I-Application
development	O
.	O
</s>
<s>
On	O
September	O
17	O
,	O
2007	O
,	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
announced	O
the	O
funding	O
of	O
a	O
new	O
internet	O
communications	O
initiative	O
with	O
David	O
Ascher	O
of	O
ActiveState	O
.	O
</s>
<s>
The	O
purpose	O
of	O
this	O
initiative	O
was	O
"	O
to	O
develop	O
Internet	O
communications	O
software	O
based	O
on	O
the	O
Thunderbird	B-Application
product	O
,	O
code	O
,	O
and	O
brand	O
"	O
.	O
</s>
<s>
On	O
February	O
19	O
,	O
2008	O
,	O
Mozilla	O
Messaging	O
started	O
operations	O
as	O
a	O
subsidiary	O
of	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
responsible	O
for	O
the	O
development	O
of	O
email	O
and	O
similar	O
communications	O
.	O
</s>
<s>
Its	O
initial	O
focus	O
was	O
on	O
the	O
then	O
upcoming	O
version	O
of	O
Thunderbird	B-Application
3	O
.	O
</s>
<s>
Alpha	O
Preview	O
releases	O
of	O
Thunderbird	B-Application
3	O
were	O
codenamed	O
"	O
Shredder	O
"	O
.	O
</s>
<s>
On	O
April	O
4	O
,	O
2011	O
,	O
Mozilla	O
Messaging	O
was	O
merged	O
into	O
the	O
Mozilla	O
Labs	O
group	O
of	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
.	O
</s>
<s>
On	O
July	O
6	O
,	O
2012	O
,	O
a	O
confidential	O
memo	O
from	O
Jb	O
Piacentino	O
,	O
the	O
Thunderbird	B-Application
Managing	O
Director	O
at	O
Mozilla	O
,	O
was	O
leaked	O
and	O
published	O
to	O
TechCrunch	O
.	O
</s>
<s>
A	O
subsequent	O
article	O
by	O
the	O
Executive	O
Chair	O
of	O
Mozilla	O
,	O
Mitchell	O
Baker	O
,	O
stated	O
Mozilla	O
's	O
decision	O
to	O
make	O
a	O
transition	O
of	O
Thunderbird	B-Application
to	O
a	O
new	O
release	O
and	O
governance	O
model	O
.	O
</s>
<s>
On	O
July	O
6	O
,	O
2012	O
,	O
Mozilla	O
announced	O
the	O
company	O
was	O
dropping	O
the	O
priority	O
of	O
Thunderbird	B-Application
development	O
because	O
the	O
continuous	O
effort	O
to	O
extend	O
Thunderbird	B-Application
's	O
feature	O
set	O
was	O
mostly	O
fruitless	O
.	O
</s>
<s>
On	O
November	O
25	O
,	O
2014	O
,	O
Kent	O
James	O
of	O
the	O
volunteer-led	O
Thunderbird	B-Application
Council	O
announced	O
on	O
the	O
Thunderbird	B-Application
blog	O
that	O
active	O
contributors	O
to	O
Thunderbird	B-Application
gathered	O
at	O
the	O
Mozilla	O
office	O
in	O
Toronto	O
and	O
discussed	O
the	O
future	O
of	O
the	O
application	O
.	O
</s>
<s>
They	O
decided	O
that	O
more	O
staff	O
were	O
required	O
working	O
full-time	O
on	O
Thunderbird	B-Application
so	O
that	O
the	O
Thunderbird	B-Application
Team	O
could	O
release	O
a	O
stable	O
and	O
reliable	O
product	O
and	O
make	O
progress	O
on	O
features	O
that	O
had	O
been	O
frequently	O
requested	O
by	O
the	O
community	O
.	O
</s>
<s>
On	O
December	O
1	O
,	O
2015	O
,	O
Mozilla	O
Executive	O
Chair	O
Mitchell	O
Baker	O
announced	O
in	O
a	O
company-wide	O
memo	O
that	O
Thunderbird	B-Application
development	O
needed	O
to	O
be	O
uncoupled	O
from	O
Firefox	B-Application
.	O
</s>
<s>
She	O
referred	O
to	O
Thunderbird	B-Application
developers	O
spending	O
large	O
efforts	O
responding	O
to	O
changes	O
to	O
Mozilla	O
technologies	O
,	O
while	O
Firefox	B-Application
was	O
paying	O
a	O
tax	O
to	O
support	O
Thunderbird	B-Application
development	O
.	O
</s>
<s>
She	O
also	O
said	O
that	O
she	O
does	O
not	O
believe	O
Thunderbird	B-Application
has	O
the	O
potential	O
for	O
"	O
industry-wide	O
impact	O
"	O
that	O
Firefox	B-Application
does	O
.	O
</s>
<s>
Mozilla	O
remained	O
interested	O
in	O
having	O
a	O
role	O
in	O
Thunderbird	B-Application
,	O
but	O
sought	O
more	O
assistance	O
to	O
help	O
with	O
development	O
.	O
</s>
<s>
Therefore	O
,	O
at	O
the	O
same	O
time	O
,	O
it	O
was	O
announced	O
that	O
Mozilla	B-Operating_System
Foundation	I-Operating_System
would	O
provide	O
at	O
least	O
a	O
temporary	O
legal	O
and	O
financial	O
home	O
for	O
the	O
Thunderbird	B-Application
project	O
.	O
</s>
<s>
On	O
May	O
9	O
,	O
2017	O
,	O
Philipp	O
Kewisch	O
announced	O
that	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
would	O
continue	O
to	O
serve	O
as	O
the	O
legal	O
and	O
fiscal	O
home	O
for	O
the	O
Thunderbird	B-Application
project	O
,	O
but	O
that	O
Thunderbird	B-Application
would	O
migrate	O
off	O
Mozilla	O
Corporation	O
infrastructure	O
,	O
separating	O
the	O
operational	O
aspects	O
of	O
the	O
project	O
.	O
</s>
<s>
Mozilla	O
brought	O
Thunderbird	B-Application
back	O
in-house	O
in	O
an	O
announcement	O
on	O
May	O
9	O
,	O
2017	O
,	O
and	O
continued	O
to	O
support	O
its	O
development	O
.	O
</s>
<s>
The	O
Thunderbird	B-Application
development	O
team	O
expanded	O
by	O
adding	O
several	O
new	O
members	O
and	O
overhauled	O
security	O
and	O
the	O
user	O
interface	O
.	O
</s>
<s>
The	O
interim/beta	O
versions	O
Thunderbird	B-Application
57	O
and	O
58	O
,	O
released	O
in	O
late	O
2017	O
,	O
began	O
to	O
make	O
changes	O
influenced	O
by	O
Firefox	B-Application
Quantum	O
,	O
including	O
a	O
new	O
"	O
Photon	O
"	O
user	O
interface	O
.	O
</s>
<s>
Despite	O
the	O
removal	O
in	O
Firefox	B-Application
Quantum	O
of	O
support	O
for	O
XUL-based	O
legacy	B-Operating_System
add-ons	I-Operating_System
in	O
favor	O
of	O
WebExtensions	B-Operating_System
,	O
the	O
stable/ESR	O
release	O
of	O
Thunderbird	B-Application
60	O
in	O
mid-2018	O
continued	O
to	O
support	O
them	O
,	O
although	O
most	O
would	O
require	O
updates	O
,	O
and	O
it	O
did	O
not	O
support	O
WebExtensions	B-Operating_System
except	O
for	O
Themes	B-Application
.	O
</s>
<s>
In	O
2018	O
,	O
work	O
was	O
underway	O
for	O
planned	O
support	O
in	O
Thunderbird	B-Application
63	O
of	O
WebExtensions	B-Operating_System
and	O
to	O
continue	O
to	O
"	O
somewhat	O
"	O
support	O
legacy	O
addons	B-Operating_System
,	O
according	O
to	O
Mozilla	O
.	O
</s>
<s>
With	O
the	O
release	O
of	O
Thunderbird	B-Application
68	O
in	O
August	O
2019	O
it	O
now	O
only	O
supports	O
WebExtension	B-Operating_System
addons	B-Operating_System
.	O
</s>
<s>
Legacy	O
Addons	B-Operating_System
can	O
still	O
be	O
used	O
if	O
a	O
special	O
"	O
legacy	O
mode	O
"	O
is	O
enabled	O
,	O
but	O
even	O
for	O
this	O
,	O
the	O
legacy	O
Addon	B-Operating_System
has	O
to	O
be	O
converted	O
.	O
</s>
<s>
Alongside	O
the	O
transition	O
,	O
OpenPGP	O
support	O
was	O
integrated	O
directly	O
into	O
Thunderbird	B-Application
as	O
a	O
standard	O
feature	O
,	O
seeking	O
to	O
supplant	O
the	O
Enigmail	B-Operating_System
extension	O
.	O
</s>
<s>
On	O
January	O
28	O
,	O
2020	O
,	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
announced	O
that	O
the	O
project	O
would	O
henceforth	O
be	O
operating	O
from	O
a	O
new	O
wholly	O
owned	O
subsidiary	O
,	O
MZLA	O
Technologies	O
Corporation	O
,	O
in	O
order	O
to	O
explore	O
offering	O
products	O
and	O
services	O
that	O
were	O
not	O
previously	O
possible	O
and	O
to	O
collect	O
revenue	O
through	O
partnerships	O
and	O
non-charitable	O
donations	O
.	O
</s>
<s>
As	O
of	O
version	O
78.7.1	O
,	O
Thunderbird	B-Application
will	O
no	O
longer	O
allow	O
installation	O
of	O
addons	B-Operating_System
that	O
use	O
Legacy	O
WebExtensions	B-Operating_System
.	O
</s>
<s>
Only	O
MailExtensions	O
are	O
now	O
compatible	O
with	O
Thunderbird	B-Application
.	O
</s>
<s>
MailExtensions	O
are	O
WebExtensions	B-Operating_System
but	O
with	O
"	O
some	O
added	O
features	O
specific	O
to	O
Thunderbird	B-Application
"	O
.	O
</s>
<s>
Thunderbird	B-Application
91	O
features	O
various	O
UI	O
improvements	O
(	O
including	O
a	O
new	O
account	O
setup	O
workflow	O
)	O
,	O
Apple	B-Device
silicon	I-Device
support	O
,	O
CardDAV	B-Protocol
address	O
book	O
support	O
,	O
built-in	O
import	O
and	O
export	O
tools	O
for	O
Thunderbird	B-Application
profiles	O
,	O
the	O
PDF.js	B-Operating_System
PDF	B-Application
viewer	O
,	O
and	O
the	O
ability	O
to	O
encrypt	O
emails	O
to	O
BCC	O
recipients	O
.	O
</s>
<s>
On	O
June	O
13	O
,	O
2022	O
,	O
it	O
was	O
announced	O
that	O
the	O
Mozilla	B-Application
Thunderbird	I-Application
team	O
would	O
take	O
over	O
development	O
of	O
the	O
Android	B-Application
email	B-Protocol
client	I-Protocol
app	O
K-9	B-Application
Mail	I-Application
,	O
with	O
plans	O
for	O
it	O
to	O
eventually	O
become	O
a	O
mobile	O
version	O
of	O
Thunderbird	B-Application
with	O
synchronisation	O
support	O
.	O
</s>
<s>
Thunderbird	B-Application
development	O
releases	O
occur	O
in	O
three	O
stages	O
,	O
called	O
Beta	O
,	O
Earlybird	O
,	O
and	O
Daily	O
,	O
which	O
correspond	O
to	O
Firefox	B-Application
's	O
Beta	O
,	O
Aurora	O
,	O
and	O
Nightly	O
stages	O
.	O
</s>
<s>
The	O
release	O
dates	O
and	O
Gecko	B-Language
versions	O
are	O
exactly	O
the	O
same	O
as	O
Firefox	B-Application
;	O
for	O
example	O
,	O
Firefox	B-Application
7	O
and	O
Thunderbird	B-Application
7	O
were	O
both	O
released	O
on	O
September	O
27	O
,	O
2011	O
,	O
and	O
were	O
both	O
based	O
on	O
Gecko	B-Language
7.0	O
.	O
</s>
