Resolving 'The specified string is not in the form required for a subject.'

Question

I have a class that sends an Email (MailMessage) but I get the following error:

"The specified string is not in the form required for a subject."

Is there a handy dandy method to sanitize the strings or do I have to write my own?

score 132 · Accepted Answer · edited Feb 20 '15 at 18:50

132

I haven't personally tried it, but according to this, you only need:

subject = subject.Replace('\r', ' ').Replace('\n', ' ');

or something equivalent.

Internally, the MailMessage class will check the subject with:

if (value != null && MailBnfHelper.HasCROrLF(value)) 
{
   throw new ArgumentException(SR.GetString(SR.MailSubjectInvalidFormat));
}

So the only limitation (for now) happens to be the presence of CR or LF.

edited Feb 20 '15 at 18:50

Ian Boyd

answered Aug 30 '11 at 07:08

Christian.K

4

Thank you for this. But gotta say -- is there any reason that Microsoft couldn't just *say* that newlines are not allowed? – Gerard ONeill Apr 05 '17 at 01:42
2

You know documentation is hard ;-) The reason it is not allowed is most likely, that CRLF has very special purposes in the message format (see [RFC5322](https://tools.ietf.org/html/rfc5322)) and they didn't wanted to bother automatically changing user's data, but rather fail and let have him do it manually (like shown above). – Christian.K Apr 05 '17 at 04:36
2

Further note `subject = subject.Replace(Environment.NewLine, " ");` – Nae Feb 20 '20 at 13:34
1

@Nae, the correct way (judging by the source code of MailMessage) is to replace BOTH `\r` and `\n` characters. Your solution will only work in some cases... – Mladen B. Feb 26 '21 at 15:33

mike nelson · Answer 2 · 2016-12-04T03:52:06.600

9

Also there is a limit of 168 characters so you should check for that too.

UPDATE: sorry this is complete bullshit :) It must have been a line break in my case.

edited Dec 04 '16 at 03:52

answered Sep 26 '12 at 07:56

mike nelson

2

Is there any documentation to link to on this? – mlhDev Aug 15 '13 at 21:24
I don't think so, we just figured it out by trial and error. I could be wrong, you are welcome to try it yourself and post the result. – mike nelson Aug 16 '13 at 04:24
Sounds good to me, I was just curious how you came by the answer (and such an odd value at that). Already +1 - a solution is a solution :) – mlhDev Aug 16 '13 at 14:02
@mikenelson - I wonder why there is such a small limit. Imagine if this is used in SSIS (An ETL tool), your package could simply fail because of this limitation. – Steam Jan 09 '14 at 00:47
I tested this with over 900 characters and it works fine – Agile Jedi Dec 01 '16 at 17:02

score 4 · Answer 3 · answered Nov 23 '12 at 08:03

4

For VB.NET

subject = subject.Replace(vbNewLine, "")

answered Nov 23 '12 at 08:03

Clarice Bouwer

3

I assumed `subject = subject.Replace(vbCr, " ").Replace(vbLf, " ")` – JNF Jan 16 '13 at 06:21

score 1 · Answer 4 · edited Dec 06 '19 at 10:54

1

I know this has already answered, but it goes:

First, you need to trim the subject then account for the subject max length (What is the email subject length limit?):

subject = subject.Trim();
subject = subject.Substring(0, Math.Min(subject.Length, 78));

This will remove any new lines or empty spaces at the beginning and the end. Then Substring is used to restrict the subject length.

edited Dec 06 '19 at 10:54

Spikolynn

answered Oct 13 '17 at 09:07

Weggo

2

Length over 78 chars is not a problem here, \r\n presence is, but nice to have this answer too. – Spikolynn Dec 06 '19 at 10:55

4 Answers4