diff --git a/__tests__/ExpensiMark-HTML-test.js b/__tests__/ExpensiMark-HTML-test.js
index 84036cb7..49280829 100644
--- a/__tests__/ExpensiMark-HTML-test.js
+++ b/__tests__/ExpensiMark-HTML-test.js
@@ -1063,3 +1063,63 @@ test('Skip rendering invalid markdown',() => {
     testString = '> *This is multiline\nbold text*';
     expect(parser.replace(testString)).toBe('<blockquote>*This is multiline</blockquote>bold text*');
 });
+
+test('Test for email with test+1@gmail.com@gmail.com', () => {
+    const testString = 'test+1@gmail.com@gmail.com';
+    const resultString = '<a href=\"mailto:test+1@gmail.com\">test+1@gmail.com</a>@gmail.com';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test for email with test@gmail.com@gmail.com', () => {
+    const testString = 'test@gmail.com@gmail.com';
+    const resultString = '<a href=\"mailto:test@gmail.com\">test@gmail.com</a>@gmail.com';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test for email with test@here@gmail.com', () => {
+    const testString = 'test@here@gmail.com';
+    const resultString = 'test@<a href=\"mailto:here@gmail.com\">here@gmail.com</a>';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test for email with test+1@here@gmail.com', () => {
+    const testString = 'test+1@here@gmail.com';
+    const resultString = 'test+1@<a href=\"mailto:here@gmail.com\">here@gmail.com</a>';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test user mention with @here@here.com', () => {
+    const testString = '@here@here.com';
+    const resultString = '<mention-user>@here@here.com</mention-user>';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test user mention with @abc_@here.com', () => {
+    const testString = '@abc_@here.com';
+    const resultString = '<mention-user>@abc_@here.com</mention-user>';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test user mention with @here_@here.com', () => {
+    const testString = '@here_@here.com';
+    const resultString = '<mention-user>@here_@here.com</mention-user>';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test here mention with @here_@here_.com', () => {
+    const testString = '@here_@here_.com';
+    const resultString = '<mention-here>@here</mention-here><em><mention-here>@here</mention-here></em>.com';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test here mention with @here@', () => {
+    const testString = '@here@';
+    const resultString = '<mention-here>@here</mention-here>@';
+    expect(parser.replace(testString)).toBe(resultString);
+});
+
+test('Test here mention with @here@here', () => {
+    const testString = '@here@here';
+    const resultString = '<mention-here>@here</mention-here><mention-here>@here</mention-here>';
+    expect(parser.replace(testString)).toBe(resultString);
+});
\ No newline at end of file
diff --git a/__tests__/Str-test.js b/__tests__/Str-test.js
index a8d92a2a..c8d1a386 100644
--- a/__tests__/Str-test.js
+++ b/__tests__/Str-test.js
@@ -77,7 +77,6 @@ describe('Str.isValidMention', () => {
         expect(Str.isValidMention('*@username@expensify.com*')).toBeTruthy();
         expect(Str.isValidMention(' @username@expensify.com')).toBeTruthy();
         expect(Str.isValidMention('~@username@expensify.com~')).toBeTruthy();
-        expect(Str.isValidMention('#@username@expensify.com')).toBeTruthy();
         expect(Str.isValidMention('_@username@expensify.com_')).toBeTruthy();
         expect(Str.isValidMention('`@username@expensify.com`')).toBeFalsy();
         expect(Str.isValidMention('\'@username@expensify.com\'')).toBeTruthy();
diff --git a/lib/ExpensiMark.js b/lib/ExpensiMark.js
index 418cc6d3..8d2186f7 100644
--- a/lib/ExpensiMark.js
+++ b/lib/ExpensiMark.js
@@ -92,12 +92,12 @@ export default class ExpensiMark {
              */
             {
                 name: 'hereMentions',
-                regex: /[`.a-zA-Z]?@here(?=_\b|\b)(?!((?:(?!<a).)+)?<\/a>|[^<]*(<\/pre>|<\/code>))/gm,
-                replacement: (match) => {
+                regex: /([a-zA-Z0-9.!$%&+/=?^`{|}_-]?)(@here)([a-zA-Z0-9.!$%&+/=?^`{|}_-]?)(?=\b)(?!(@[a-zA-Z0-9-]+?(\.[a-zA-Z]+)+)|((?:(?!<a).)+)?<\/a>|[^<]*(<\/pre>|<\/code>))/gm,
+                replacement: (match, g1, g2, g3) => {
                     if (!Str.isValidMention(match)) {
                         return match;
                     }
-                    return `<mention-here>${match}</mention-here>`;
+                    return `${g1}<mention-here>${g2}</mention-here>${g3}`;
                 },
             },
 
@@ -110,7 +110,7 @@ export default class ExpensiMark {
              */
             {
                 name: 'userMentions',
-                regex: new RegExp(`[\`.a-zA-Z]?@+${CONST.REG_EXP.EMAIL_PART}(?!((?:(?!<a).)+)?<\\/a>|[^<]*(<\\/pre>|<\\/code>))`, 'gm'),
+                regex: new RegExp(`[a-zA-Z0-9.!$%&+/=?^\`{|}-]?@+${CONST.REG_EXP.EMAIL_PART}(?!((?:(?!<a).)+)?<\\/a>|[^<]*(<\\/pre>|<\\/code>))`, 'gm'),
                 replacement: (match) => {
                     if (!Str.isValidMention(match)) {
                         return match;
diff --git a/lib/str.js b/lib/str.js
index 14a582f0..ad48560e 100644
--- a/lib/str.js
+++ b/lib/str.js
@@ -943,8 +943,16 @@ const Str = {
      * @returns {bool}
      */
     isValidMention(mention) {
-        // A valid mention starts with a space, *, _, #, ', ", or @ (with no preceding characters).
-        return /[\s*~_#'"@]/g.test(mention.charAt(0));
+        // Mentions can start @ proceeded by a space, eg "ping @user@domain.tld"
+        if (/[\s@]/g.test(mention.charAt(0))) {
+            return true;
+        }
+
+        // Mentions can also start and end with a *, _, ~, ', or " (with no other preceding characters)
+        // eg "ping *@user@domain.tld*"
+        const firstChar = mention.charAt(0);
+        const lastChar = mention.charAt(mention.length - 1);
+        return /[*~_'"]/g.test(firstChar) && /[*~_'"]/g.test(lastChar) && firstChar === lastChar;
     },
 
     /**