Exim cPanel has an issue when sending emails using ms outlook and make sure this is the latest exim, Exim 4.95;
"1nBxPK-0023Ax-M1** email@example.com R=dkim_lookuphost T=dkim_remote_smtp: message has lines too long for transport"
a. The whm/cpanel server only uses the hosting server SMTP and does NOT use or use the smarthost relay configuration using Spamexperts etc., then simply run the update below:
b. Whm / cpanel server USES relay smarthost SMTP Spamexperts, then please go to WHM> Exim Configuration Manager> Advanced Configuration Manager and add the line below at the end of the @TRANSPORTSTART line / section
message_linelength_limit = 2048