[quote user="jonm"]As I said at 5906 characters the line becomes invisible so I find your statement of 16kb doesn't match my reality.[/quote]

Becoming invisible doesn't necessarily mean you can't enter more. I just pasted in more than 6000 characters which made Pegasus Mail throw a (software) exception which didn't crash it, though. And if copying all of it back to my text editor it still contains all of them while I even can type in more (without the line end getting blank) ... But I can duplicate the error message when trying to send a message with such a long line. This might be an internal processing error (truncation for not exceeding buffer size), though, since the editor field seems to accept more characters.

Tried searching but didn't find anything, so if it has been covered please point me to discussion.

Someone sent me an email with a very long list of addresses and when I tried to reply all pmail said an email address was invalid.

I wondered if the list was too long so I constructed an email with a longer and longer list in it.

When the list got to 5906 characters the to line went blank but I could still do a "home" and "end" on the To line and the cursor moved to it's start and end. Deleting characters did not redisplay the list. 

A Ctrl-A and Ctrl-C on the To line also produced nothing when I pasted into a text editor.

 Is this a known issue  in 4.70 or I have got something wrong?

[quote user="jonm"]Someone sent me an email with a very long list of addresses and when I tried to reply all pmail said an email address was invalid.[/quote]

I don't think the length of the address list matters here when the error message says there's an invalid address. So how about figuring out which one (such as an adress with an alias including commas without being enclosed in quotes, e.g.: last name, first name <email address> instead of the proper "last name, first name" <email address>)?

Apologies.

Didn't make it clear. It was the number of characters allowed in a To line I was asking about.

[quote user="jonm"]Didn't make it clear. It was the number of characters allowed in a To line I was asking about.[/quote]

Why would it matter? I believe it's 16 KB but I can't tell for sure.

Aside from this one should rather use a distribution list instead of piling up all addresses on the To: line, not the least because of privacy protection since you always disclose the whole list to all recipients ...

Your comment is not always true and is one of the reasons I wanted to check the maximum length of the To line. As I said at 5906 characters the line becomes invisible so I find your statement of 16kb doesn't match my reality.

Gmail for instance allows you to have a "list" but puts all the email addresses visibly in the To line. This is important if you want to allow people to know who has been sent the email.