validate email address without Regex

Thanks to Mike Schmitt there is existing code.

community.appian.com/.../way-to-validate-email-addresses

After reading this

https://stackoverflow.com/questions/2049502/what-characters-are-allowed-in-an-email-address

I think that email address validation is pretty ugly and not doable without regex. In case you want to rule out the most simple typos, then go with Mikes code. I just updated it to comply with latest changes in Appian

a!localVariables(
  local!trimmed: trim(ri!address),
  if(
    or(
      isnull(local!trimmed),
      len(local!trimmed) > 255,
      length(split(local!trimmed, " ")) > 1,
      count(split(local!trimmed, "@")) <> 2
    ),
    false(),
    a!localVariables(
      local!localPart: split(local!trimmed,"@")[1],
      local!domainPart: split(local!trimmed,"@")[2],
      if(
        or(
          length(split(local!domainPart, ".")) < 2,
          contains(split(local!localPart, "."), ""),
          contains(split(local!domainPart, "."), ""),
          not(isnull(stripwith(lower(local!domainPart), "abcdefghijklmnopqrstuvwxyz1234567890-."))),
          not(isnull(stripwith(lower(local!localPart), "abcdefghijklmnopqrstuvwxyz1234567890-._+'&%")))
        ),
        false(),
        true()
      )
    )
  )
)

Thanks !  The above code, as its own expression rule, has helped me out in various different Appian projects since I originally wrote it, especially those where we didn't (yet) have the RegEx plug-in.  For what it's worth, since then I've swapped it out with the actual RegEx functionality as it's able to handle a little bit more.  saurabh sharma is there a reason you can't use the RegEx plug-in?

Here's the current code (still in an expression rule i.e. `UTIL_isValidEmailAddress()`) --

regexmatch(
  pattern: "^[A-Z0-9\_-]+(\.{0,1}[A-Z0-9\+_-]+)*[@]{1}[A-Z0-9.-]*[A-Z0-9-]+[.]{1}[A-Z]{2,6}$",
  searchString: ri!email,
  regexFlags: "si"
)

I'm usually the one to jump on "you're using Regex WAY too quickly" but in this case, it looks like regex is much more efficient.

Unless Appian comes out with a "isValidEmail" function out of the box, regex may be your best bet.

Unknown said:

Unless Appian comes out with a "isValidEmail" function out of the box

Yeah, and I've always been a little confused as to why this isn't just a usable function, because various places within Appian *certainly* do seem to do their own validation on proper email address formatting.

Edited to add (2023-02-13), the People Functions plug-in now has an email address validation function built-in, and it passes all the same test cases that I use against my RegEx version above, if this helps anyone.  Once again I beg everyone not to avoid using plug-ins for arbitrary reasons, they are in many cases essential to not having to reinvent the wheel over and over again.

How to show a custom error message when the validation doesn't pass?

Did you try to use the validations parameter of your text field?