I have looked all over the internet, and i'm pretty good at finding things and have not seen an answer to this issue with Mac users specifically. I work in a corporate environment and send emails all day with a signature that has two logos as images in it. I have had a few people tell me that my signature causes issues with this outlook when they reply to me, that it is looking for the images from my signature. As seen in the attachment, this takes a while and for some even crashed their outlook.
All that I can find is that for Windows there is a Registry key that can be changed to 'Send picture with document' that fixes this issue. I can't find anything in the settings in Outlook and wouldn't know how this Registry trick translates for Mac. Office for mac 2016 review. Please help as this keeps causing lots of issues. Hi Patrick, Thank you for contacting us. From my understanding, when the mac users reply your email with the signature, their Outlook for Mac client will take a long time to look for the images your signature contained and even cause crash.
How to install your htmlsig.com email signature on Microsoft Outlook 2016 Mac in just a few steps. Music by Joakim Karud http://soundcloud.com/joakimkarud.
Microsoft Outlook 2016 For Mac
For this issue, I suggest you take the following measures to check if it works. Free pop3 email accounts for outlook express. Confirm if the recipients could successfully reply your emails in Outlook web side. Office 365 account please check it in OWA (), Outlook.com account please click. If it’s workable, please regard it as a temporary workaround.
Check if their Outlook for Mac client is the latest version, you can refer to and make a contrast. Also, if there’re add-ins in their Outlook for Mac client, please disabled them and check if it works. 
If the issue still exists, for better help you, I suggest you contact in-app support by clicking Help > Contact Support button in Outlook for Mac client. There will be our dedicated engineers providing further assistance for you.
Outlook 2016 Signature Not Working
Regards, Marvin.