Bug#828801: Legitimate mail can contain long lines

[Gedalya]

On 12/17/2016 11:48 AM, Andreas Metzler wrote:
> Control: tags -1 pending
>
> exim4 (4.88~RC6-2) UNRELEASED; urgency=medium
>  .
>    * Add macro MAX_PHYSICAL_LINE_LENGTH with a default value of 998 to allow
>      overriding the SMTP physical line length limit both for SMTP DATA ACL and
>      remote_smtp* transports. Closes: #828801
>      Also update corresponding NEWS entry.

The correct limit is 998 octets. If my incoming mail flow violates this, it would be because the sender does not have a defined line length limit.
How then can I come up with a number to set this variable to?
An arbitrary figure such as 9999 might just happen to work, but wouldn't it be better to make it possible to revert to the previous behavior, and skip this check entirely?