Phone number in email is flagged by Gmail as SPAM

Emails that include a specific office number sent from GoDaddy Office 365 are being flagged by Gmail as SPAM.

When I send emails that do not include this specific office number, emails are delivered to the Gmail users Inbox.  When the body or email signature includes the extension 8305, gmail will deliver the email to the SPAM folder.  I have tried all different variations, including bracketx, dots, hyphens, spaces, etc... when you add the entire number, the email is sent to the Gmail SPAM folder.  I have even swapped out the numbers, and the email is delivered perfectly.  Its only with the 8305 extension is added to the email, that gmail decides to filter and deliver the mail to the SPAM folder.  

Also, when I test and send the exact email from my on-prem Exchange 2010 box, the email is delivered properly to the gmail Inbox.  I was leaning more towards Google being the issue, but it seems to be GoDaddy Office related.  What exactly should I be looking for? In my research, I see posts to ensure that my SPF and DKIM are setup properly.  I have checked MXtoolBox and everything comes back OK.  Not sure what else to check?  Any suggestions?
Riky SerranoIT Support ManagerAsked:
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Michael FowlerSolutions ConsultantCommented:
Have you tried making the phone number a telephone link e.g. tel:+61299998305
Riky SerranoIT Support ManagerAuthor Commented:
No luck :(  I tried adding just the + and then adding +1 (US code).
Dr. KlahnPrincipal Software EngineerCommented:
Possible alternative:  Use a digits-to-GIF converter and include the phone numbers as images.  Has two advantages:

a) The contents won't be examined
b) If email is misdelivered to a spam trap, that info may not be read and added to a spammer database.
Owen RubinConsultantCommented:
So just as a test, I sent myself an email with a bunch of 8305 in the text to another Gmail account. It was not bothered by the 8305.

All I can assume here is that something in your message is on the edge, and something about 8305 pushes it over. I did a Google search on 8305, and maybe mixed with other words in your email, one or more of those results pushes it over some threshold Google has set.

I would say send it to Google, but I do not believe they offer support on Gmail.

Can we get a copy of the whole email? I would like to send it to myself (or you can send it to me) and see if it gets flagged here as well.
Mal OsborneAlpha GeekCommented:
Generally, spam filters use a "points" based system, examining myriad different parameters that may look spammy. This might include multiple recipients in alphabetical order, an overseas email address, words like "Viagra" or "opportunity"   etc. Looks like your phone number is also considered point worthy. A certain amount of points and the email is considered spam.

It may be difficult to do much about the phone number, however here are a heap of other things you can do. SPF,  DKIM and DMARK are a few big ones, (listed in order of importance).

The next step I would advise is to browse to https://www.mail-tester.com/ This site will give you an email address, you send it a message, and it will do an extensive analysis, reporting back anything that might look spammy. It is free. Should it report back something you don't understand, post it here, and someone will assist.
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