As the title suggests, some recipients aren't receiving emails from our company. This has been going on for just over a week - apart from today's server issues; emails are sending okay and have the 'delivered' button but upon checking with the recipient, the email isn't landing in their inbox - this is several different email addresses form different organisations.

One organisation reported the emails had been received but were stuck in quarantine. This has never happened before. I've updated a TXT record with SPF record and all is pointing the right way but i'm wondering if this is a spam issue? or encryption issue? could it be to do with a link in a new email signature that i've seen reported as an issue before?

I'm unable to take this any further - some recipients are receiving the emails and some aren't. Some emails are being received and some aren't yet nothing is stuck in our quarantine. 

Does anyone have any ideas? To recap - This might be a spam filtering issue but I don't know what is making our emails dodgy. Might be to do with a link in the email signature? Would appreciate a reply from ZOHO.