Our software is parcing the mail from people and I wanted to include some breakline in their email when they reply to help identify "original message" and cut them out for the sake of clearance.
Normally in outlookk, when I reply letter of certain, I can see "----Original Message---" automatically appears at the top of old/original message. But not for some other letters. There is no '---Original Message---" but a <hr> only.
I guess this may be related to header of the mail or something.
This is entirely due to the mail client that the person replying is using - different clients handle the formatting of the response differently. Thunderbird, for example, prefixes each line with a ">".
If you're trying to programmatically remove the original message, you're probably going to have to investigate a number of the most common clients and write custom code for each. Fortunately, you can use the User-Agent: header to determine what client sent the response and use that to guide your selection of which parsing code to use for each message.
If this is about opening email in Outlook and such programs, I don't know if this is the correct forum to seek advice about it (less people will know what this question is about). For example, I was under the impression you were asking about a mailing script and how to insert a line break so the recipient sees it in the format you desire. Unfortunately for the question, I've not used Outlook in 15 years or something and I'm assuming the <hr> is due to them sending in HTML format and Outlook not keeping your preferences in the reply formatting, but that of the sender's preference.
Thanks, I thought so too that the breakline is determined by client mail software.
I gave it a short-cut by clumsy solution. When I send email to my customer , I put under my message always a break line ( a line of text ### please reply above here###), and when he replied me, I will at least be able to block most of the old messages under my line.