What is the format accepted by System.Net.Mail.MailAddress' parser?

Question

I'm working on an app that's using System.Net.Mail.MailAddress and friends for sending emails. Does that parser implement the full RFC5322 or a subset or what? The MSDN is not very forthcoming on this topic.

Any hints appreciated.

Answer 1

I've wrote a little snippet to test the function:

foreach (int i in Enumerable.Range(32,128-32))
{
    char c = (char)i;
    string addr = String.Format("par.t1{0}pa.r{0}[email protected]", c);
    try
    {
        var mailAddr = new MailAddress(addr);
    }
    catch
    {
        Console.WriteLine("MailAddress failed '{0}' ({1}): {2}", c, i, addr);
    }
}

With the following results on 3.5 SP1:

MailAddress failed ' ' (32): par.t1 pa.r [email protected]
MailAddress failed '"' (34): par.t1"pa.r"[email protected]
MailAddress failed '(' (40): par.t1(pa.r([email protected]
MailAddress failed ')' (41): par.t1)pa.r)[email protected]
MailAddress failed ',' (44): par.t1,pa.r,[email protected]
MailAddress failed ':' (58): par.t1:pa.r:[email protected]
MailAddress failed ';' (59): par.t1;pa.r;[email protected]
MailAddress failed '<' (60): par.t1<pa.r<[email protected]
MailAddress failed '>' (62): par.t1>pa.r>[email protected]
MailAddress failed '@' (64): [email protected]@[email protected]
MailAddress failed '[' (91): par.t1[pa.r[[email protected]
MailAddress failed '\' (92): par.t1\pa.r\[email protected]
MailAddress failed ']' (93): par.t1]pa.r][email protected]
MailAddress failed '⌂' (127): par.t1⌂pa.r⌂[email protected]

Also it doesn't seem to support "quoted-string" local-parts, like "blah"@example.com.

I don't think a validator could accept any less before becoming unusable.

Answer 2

In the discussion thread on Dominic Sayers isemail article, Jerry O'Brien said that he read Dominic's RFC compliance test cases against the System.Net.MailAddress class:

System.Net.MailAddress is only 59% compliant with the RFC specifications. Follow-up comments noted the specific cases where it generated false positives and false negatives.

The RFCs are extremely weak on what constitutes a valid email email address. They allow a range of unusual and unpopular formats. So I guess the real question is, is System.Net.MailAddress good enough in a majority of real-world situations?