#slack-inputgroup {
  border: 1px solid #eee;
  border-radius: 5px;
  margin: 15px 0;
  clear: both;
  display: inline-block;
}
#slack-email-inputfield {
  border: none;
  padding: 5px 10px;
  color: #333;
  font-size: 14px;
  line-height: 26px;
  outline: none;
  background: #efefef;
  width: 200px;
}
#slack-email-label {
  font-weight: 600;
  border-radius: 5px;
  display: block;
}
#slack-submit-button {
  border: none;
  color: #fff;
  background: darken($blue, 10%);
  padding: 10px 15px;
  border-radius: 0 5px 5px 0;
  cursor: pointer;

  &:active {
    outline: none;
  }

  &:hover {
    background: darken($blue, 5%)
  }
}
#slack-error {
  color: #d60f07;
  font-weight: 500;
}
#slack-inputgroup {
  border-radius: 5px;
  margin: 15px 0;
  clear: both;
  display: inline-block;
}
#slack-email-inputfield {
  border: none;
  border-radius: 5px 0 0 5px;
  padding: 5px 10px;
  color: #333;
  font-size: 14px;
  line-height: 26px;
  outline: none;
  background: #efefef;
  width: 200px;
}
#slack-email-label {
  font-weight: 600;
  border-radius: 5px;
  display: block;
}
#slack-submit-button {
  border: none;
  color: #fff;
  background: darken($blue, 10%);
  padding: 10px 15px;
  border-radius: 0 5px 5px 0;
  cursor: pointer;

  &:active {
    outline: none;
  }

  &:hover {
    background: darken($blue, 5%)
  }
}
#slack-error {
  color: #d60f07;
  font-weight: 500;
}
Remove border on slack invite input field
Remove border on slack invite input field
