>Anyone would know the regulation for the maximum length of a subject in an email? Is it something general or specific to the mailer/servers? I have an email which I need to include specific IDs in the subject and this one is quite long. I am have 134 character so far and this is accepted. However, do I have a guarantee that this will make it to the destinator?

According to RFC 2822
http://www.faqs.org/rfcs/rfc2822.html
...""There are two limits that this standard places on the number of characters in a [email message] line. Each line of characters MUST be no more than 998 characters, and SHOULD be no more than 78 characters, excluding the CRLF."...."

Of course the problem is that many services ignore that -AOL cuts it off a 60, HotMail is 45, Yahoo is 47, etc etc etc...and just to make things more difficult there are also limitations in the client software sometimes too - so Thunderbird VS Outlook can be different.