URL at the beginning of a line in plain text body isn't linkified
This happens because we first convert the plain text to HTML and end up with something like:

```html
<br>http://uri.example.org<br>
```

But right now only supported schemes preceded by a space, a newline, or an opening parenthesis are candidates for linkifying.

https://github.com/k9mail/k-9/blob/27bc562ebe37bc139b84c13142681dbfe5640688/k9mail/src/main/java/com/fsck/k9/message/html/UriLinkifier.java#L16
diff --git a/k9mail/src/main/java/com/fsck/k9/message/html/UriLinkifier.java b/k9mail/src/main/java/com/fsck/k9/message/html/UriLinkifier.java
index 815acc5ce..3d2565f27 100644
--- a/k9mail/src/main/java/com/fsck/k9/message/html/UriLinkifier.java
+++ b/k9mail/src/main/java/com/fsck/k9/message/html/UriLinkifier.java
@@ -13,7 +13,7 @@ import android.text.TextUtils;
 public class UriLinkifier {
     private static final Pattern URI_SCHEME;
     private static final Map<String, UriParser> SUPPORTED_URIS;
-    private static final String SCHEME_SEPARATORS = " (\\\\n";
+    private static final String SCHEME_SEPARATORS = " (\\\\n>";
     private static final String ALLOWED_SEPARATORS_PATTERN = "(?:^|[" + SCHEME_SEPARATORS + "])";
 
     static {
diff --git a/k9mail/src/test/java/com/fsck/k9/message/html/UriLinkifierTest.java b/k9mail/src/test/java/com/fsck/k9/message/html/UriLinkifierTest.java
index 3b02dc035..81abbbb34 100644
--- a/k9mail/src/test/java/com/fsck/k9/message/html/UriLinkifierTest.java
+++ b/k9mail/src/test/java/com/fsck/k9/message/html/UriLinkifierTest.java
@@ -136,4 +136,13 @@ public class UriLinkifierTest {
                         "<a href=\\"http://uri2.example.org/path\\">http://uri2.example.org/path</a> postfix",
                 outputBuffer.toString());
     }
+
+    @Test
+    public void uriSurroundedByHtmlTags() {
+        String text = "<br>http://uri.example.org<hr>";
+
+        UriLinkifier.linkifyText(text, outputBuffer);
+
+        assertEquals("<br><a href=\\"http://uri.example.org\\">http://uri.example.org</a><hr>", outputBuffer.toString());
+    }
 }
['k9mail/src/test/java/com/fsck/k9/message/html/UriLinkifierTest.java', 'k9mail/src/main/java/com/fsck/k9/message/html/UriLinkifier.java']