Reply to topic -> PHP error

This happens randomly when replying to topics (probably ones that someone has subscribed to?), although the post still goes through:

Deprecated: Function split() is deprecated in /home/hbc-www/forum.wiibrew.org/mods/smtp_mail/swiftmailer/Swift.php on line 285

Deprecated: Function split() is deprecated in /home/hbc-www/forum.wiibrew.org/mods/smtp_mail/swiftmailer/Swift.php on line 285

Deprecated: Function split() is deprecated in /home/hbc-www/forum.wiibrew.org/mods/smtp_mail/swiftmailer/Swift.php on line 285

Deprecated: Function split() is deprecated in /home/hbc-www/forum.wiibrew.org/mods/smtp_mail/swiftmailer/Swift.php on line 285
There was a problem communicating with SMTP: Expected response code(s) [250] but got response []

Yeah, it's been that way for a while. It doesn't really matter though, the posts still work.