<s>
Spark	B-Protocol
is	O
an	O
email	O
application	O
for	O
Windows	O
,	O
iOS	B-Application
,	O
macOS	B-Application
,	O
and	O
Android	B-Application
devices	O
by	O
Readdle	O
.	O
</s>
<s>
Lifehacker	O
wrote	O
that	O
Spark	B-Protocol
was	O
the	O
best	O
alternative	O
for	O
Mailbox	B-Protocol
users	O
when	O
that	O
service	O
went	O
offline	O
.	O
</s>
<s>
On	O
April	O
2	O
,	O
2019	O
,	O
Readdle	O
released	O
Spark	B-Protocol
for	O
Android	B-Application
,	O
the	O
company	O
's	O
first	O
mobile	O
application	O
for	O
the	O
Android	B-Application
platform	I-Application
.	O
</s>
